The night of the graduation exercises at the Bayport high school arrived, differing little from similar events in past years but of profound importance to the members of the graduating class and their parents.

Mr. and Mrs. Hardy were there, very proud of their two boys, and Mrs. Hardy beamed with pleasure when Frank and Joe, dressed in their finest clothes and looking very uncomfortable, stepped up to receive their diplomas. Chet Morton was so nervous and embarrassed that he stumbled on the way to the platform and ended by dropping the diploma when it was handed to him.

All the girls looked their prettiest, the boys looked their handsomest, the principal of the school excelled himself in the speech he had made at every graduation for the past fifteen years, various prominent citizens expressed their pride in the young people, and Callie Shaw, as class valedictorian, won the hearts of all by her valedictory address.

There were other numbers on the program, including a violin solo by Iola Morton, an exceedingly vigorous recitation by Biff Hooper, an accordion solo by Tony Prito and—to cap it all—the antics of a burlesque orchestra organized by Chet. In this, Chet was in his element, wearing a fireman’s hat and a huge false mustache. Frank and Joe Hardy, wearing stovepipe hats and red wigs, alternated at a bass drum; Jerry Gilroy, in a coat that reached to his heels, performed upon a saxophone that wouldn’t work and from which Chet produced a string of sausage at the critical moment; Phil Cohen tortured a flute that was capable of but one note. The burlesque orchestra assaulted the ears of the audience for some time, with no music whatever, but with such earnestness that the hearers were doubled up with laughter.

This was the high spot of the program, so far as the boys were concerned, and it ended the graduation exercises. When they left the school that night they all felt a little sad, as they knew they were leaving it for all time, “unless,” Chet Morton said, “they invite us back some day when we’re very famous to address the students on ‘The Secret of Success.’ ”

“In the meantime,” said Frank, “what are we going to do this summer?”

“I’d like another outing,” Joe volunteered.

“Too much excitement for me,” returned Chet. “Last summer we were going to have a nice quiet trip down the coast, and look what happened. We got mixed up with a gang of smugglers and had no end of trouble.”

“It finished up happily enough, didn’t it?” said Frank. “Even if you did get lost!”

“This summer, I’d like to have a nice quiet holiday in a nice quiet cabin, with a good beach, where we can swim and loaf around and eat and sleep and not have anything to worry about.”

“Sounds attractive,” Joe admitted. “Where are you going to find this place, and how can we get there?”

“How about Cabin Island?” suggested Biff Hooper.

The others were thoughtful.

“You’ve had worse ideas, Biff,” said Chet Morton. “Do you think Mr. Jefferson will let us go there?”

Frank laughed.

“Why not? Didn’t we find his missing stamp collection? Didn’t he say we could have the use of the island and the cabin any time we wished? There won’t be any trouble so far as that’s concerned.”

“I think an outing to Cabin Island would be the real thing,” Joe declared. “What do you say to organizing a trip? We can take the motorboats, use Cabin Island as our headquarters, then work out from there so we can go wherever we wish.”

“You have a head on your shoulders,” Chet approved. “When we get tired of camping we can go exploring. When we get tired of the motorboats we can loaf around Cabin Island.”

“Joe and I have the summer free,” said Frank. “After that, we’ll either go to college or go into business with our father.”

“Don’t you know yet?”

“We want to go in with dad,” said Joe promptly. “But he and mother seem bent on having us go to college. I think we’ll have a lot of arguing yet.”

“In the meantime, don’t let it spoil your summer,” advised Chet. “Well, if you want to go on this outing, be sure and count me in. We can dig up some of the other fellows and we ought to have a bang-up good time.”

“You can’t dig up many of them,” came from Joe.

“Why not? Any fellow ought to jump at a chance like that.”

“Well, some of them wouldn’t be allowed to leave home—got to work and all that. And some are on the ball team and have to practice when they aren’t playing a game. And Dick Roylet and his crowd are going on an auto tour.”

“Well, we’ll get somebody—if we go,” put in Frank.

Next day when the Hardy boys told their parents about the outing they had planned, Mr. and Mrs. Hardy glanced at one another.

“Don’t you think you had better be making your preparations for going to college?” suggested Mr. Hardy.

“If you wait too long, perhaps you may not be able to get in,” their mother ventured.

“Do we have to go to college?” asked Frank.

Mr. Hardy looked dubious.

“You know, your mother and I have always had that in mind for you.”

Joe groaned.

“I’ll make a rotten lawyer.”

“And I’m sure I’ll be a pretty punk doctor,” declared Frank. “Dad, won’t you let us go into business with you? We like detective work. It’s the only thing we’ll ever be happy at. Haven’t we done fairly well with the cases we’ve had so far?”

“Yes, you’ve done well. I’ll admit that. Still—I think I’d rather see you go in for something else.”

“Would you want us to go in for something we wouldn’t enjoy?” said Joe. “A person can’t be a success in his work unless he really likes it.”

“That’s true,” returned Mr. Hardy, weakening a little. “Well, I must have time to think it over.”

Frank offered a suggestion.

“Let us go on our outing first, and by the time we come back we can settle the whole thing. We’ll be back in plenty of time to go to college, if you really insist that we go.”

Mrs. Hardy nodded. “I think that’s fair enough, Fenton,” she said to her husband.

“All right, then,” agreed the detective. “We’ll let the matter rest for the time being, and as soon as you boys return from your trip we’ll go into it thoroughly. But you must promise to abide by my decision. I don’t want to send you to college against your will, but I do want to do what’s best for your future.”

“We understand that,” said the boys. “It’s for our own good. But we do want to be detectives.”

Mr. Hardy smiled.

“You seem to have your minds made up, at any rate. Well, let it go at that. Have your outing and enjoy yourselves. Then we’ll settle the whole matter, once and for all.”

However, the lads had little time in which to proceed with their plans for the outing. They did not see Chet Morton that afternoon and the trip was not discussed with any of the other lads they met. Next morning, as they were having breakfast, their father came into the dining room.

“After breakfast is over,” he said, “come into my study. I want to have a little talk with you.”

“We’ll be there.”

When their father had gone, they fell to wondering why he wanted to see them.

“I can’t think of any mischief we’ve been into—except breaking that pane of glass in the garage,” said Joe.

“He wouldn’t scold us for that. I intended to put in a new pane of glass to-day.”

“There’s something in the wind.”

They hurried through the remainder of the meal, anxious to learn the reason for the summons. When they went into the study, Mr. Hardy was reading a long typewritten letter which he placed to one side.

“I’ve been asked to handle a case,” he explained at once, “and I thought maybe you could help me a little. Sometimes you hear of things that I mightn’t learn about. This is a serious case and just now I’m trying to make up my mind how to go about it.”

“What has happened, Dad?” asked Frank.

“I received this letter this morning from the postal authorities, explaining the circumstances. It seems that several bags of valuable mail have disappeared from one of the hangars at the airport near here.”

“Stolen?”

“They couldn’t have disappeared any other way. The mail, as you know, is very carefully guarded. In this instance, the train that was to take the mail into the city was a few minutes late and the sacks were accidently left unguarded. When the train arrived it was found that the mail had disappeared. The matter is being kept quiet for the time being, in the hope that we may get a clue. But so far the whole business seems to be a complete mystery.”

“Haven’t they any idea who stole it?” asked Joe.

“No idea at all. The only men around, so far as they know, were the usual airport officials and pilots. Practically all of them are above suspicion. From the looks of the case, I’m inclined to think some outsider may have been hiding near by, watching his chance, and when he saw the sacks left unguarded he simply seized them and cleared out.”

Frank leaned forward in excitement.

“I think we can help you a little,” he declared. “We may know something about that very robbery.”

“Already?” exclaimed Fenton Hardy, astonished.

Frank and Joe thereupon told their father about their adventure in Beach Grove on the day of the picnic. They told that they had seen Giles Ducroy and his two companions near the old cabin, how they had followed the men and listened to their conversation.

“Ducroy was trying to get these other chaps to go in with him on some crooked deal, and they were afraid because they said it was too dangerous,” explained Frank. “Ducroy told them they’d make ten thousand dollars apiece out of it. Perhaps that was what he meant. He planned to steal some of the mail bags.”

Fenton Hardy was interested.

“Certainly a suspicious conversation,” he admitted. “Still, the mail bags weren’t worth any thirty thousand dollars, if what the post office people tell me is correct. They were worth about two thousand dollars at the most. Besides, Giles Ducroy is already under suspicion.”

“Has he been arrested?” asked Joe.

Fenton Hardy shook his head.

“When the theft occurred, the authorities first thought of Ducroy, because they knew he had been discharged and was probably looking for a chance of revenge. So their first action was to investigate his movements on the day of the robbery.”

“And what did they find?”

“He wasn’t near Bayport at all. He was in Philadelphia—at least, he has such an alibi.”

“Can he prove it?” asked Frank.

“He had two witnesses to prove it. So nothing could be done against Ducroy.”

“I’d like to know who those witnesses were,” said Frank. “I don’t believe he was in Philadelphia at all.”

The boys were openly dubious about Ducroy’s alibi.

“He’s a slick one, Dad,” declared Joe. “He may look dumb, but he’s not as dumb as he looks.”

The news that Giles Ducroy had a proven alibi to clear himself of suspicion in the affair of the stolen mail sacks disconcerted the Hardy boys for a time.

When their father told them about the robbery their first thought was that Ducroy and his two companions were the guilty parties, for the theft seemed to be linked up in some manner with the conversation the lads had overheard in the cabin at Beach Grove. However, there now remained the fact that Ducroy had an alibi, and also the fact that the mail sacks were by no means worth the amount the former pilot had mentioned to his companions.

“Just the same,” declared Frank that afternoon, “I’m convinced that Ducroy had something to do with the affair, alibi or no alibi.”

“Perhaps the mail sacks weren’t stolen by Ducroy,” suggested Joe. “Perhaps he went to Philadelphia, so he would be able to prove an alibi, and left Newt Pipps and Ollie Jacobs to commit the actual robbery.”

“It could have been worked that way. I’ll tell you what we’ll do, Joe. Let’s take the roadster and drive back down to Beach Grove. I’d like to take another look at that cabin. Perhaps we’ll find a few clues there that may help us.”

Joe was impressed by this suggestion, and in a short time the Hardy boys were speeding down the Shore Road in their car. When they reached the grove they left the roadster and made their way through the woods down the path toward the little cabin.

“We didn’t have the opportunity to look through the place when we were here before,” Frank pointed out. “They may have left something behind, a few notes or plans for instance, that will give us a better idea of what they were talking about.”

“It’s a mighty suspicious thing that a robbery should occur at the airport so soon after Giles Ducroy and his friends were talking about some crooked scheme.”

“That’s the way I feel about it.”

The boys entered the cabin. The door was unlocked and the place was deserted. It was sparsely furnished with only a small wooden table, two broken chairs and a few boxes.

“Nothing much here,” Frank remarked. “Still, it won’t do any harm to look around carefully.”

Joe came upon an empty bottle over in a corner, perhaps the bottle from which the men had been drinking on the afternoon of the picnic. Frank’s attention was attracted by a number of cigarette stubs on the table.

“Sometimes a little thing like a cigarette turns out to be a mighty valuable clue,” he observed, examining the stubs. Most of them were very short, but on one, a trifle longer than the rest, he found the letters “RE.” The rest of the word had been obliterated with the burning of the cigarette.

“I wonder what make of cigarettes they were smoking,” he said. He searched the cabin thoroughly and at last he found what he was looking for. Beneath one of the boxes he saw a crumpled paper package. He picked this up, unfolded it, and examined it carefully.

The package had once held cigarettes, and across the front he saw the name, “Red Ribbon Cigarettes.”

“Not much of a clue there,” laughed Joe. “All gone up in smoke.”

“You never can tell,” returned his brother, pocketing the package.

“Better be careful. If mother finds that package in your pocket she’ll think you’ve been smoking.”

“Mother knows us well enough to know we don’t smoke,” Frank said. “I have a hunch that this little package may come in handy some day.”

Although the boys searched the bare little cabin high and low, they found nothing else that might help them. Their search for clues appeared to have been a failure.

“Ducroy and his friends were too wise to leave any notes that might incriminate them,” Joe said, as they went away. “I guess we’ll have to tackle the case from another angle.”

“Dad’s handling it to the best of his ability, and I guess he will be in a position to get information that we’ll never run across. All we can do is to keep our ears open and, if we hear anything, let him know.”

The boys returned to Bayport, somewhat disappointed; but when they were near their home they dismissed the mail bag mystery from their minds, for they met Chet Morton and Biff Hooper.

“Just who we were looking for!” exclaimed Chet. “We called at the house, but your mother said you had gone out.”

“What’s up?” asked Joe.

“Why, Biff and I thought it would be a fine afternoon to take a little boat trip. I thought we could go down to Cabin Island and see that everything is in shape. We can find out what we need to take down there for our outing. I know we left some kitchen dishes and other things there last winter, but they may be gone by now. We can look the place over and make a list of what we’ll have to bring along.”

“You’re going on the trip, aren’t you?” asked Biff.

“Sure, we’re going. I guess it isn’t too late in the day to go down to the island, Chet. Come on with us and we’ll take the car back to the garage.”

The Hardy boys drove back to the house with the other lads, told their mother that they were going down to Cabin Island in the boat, and started off for the boathouse. The lads did not take any food with them, for the Hardy boys’ motorboat, The Sleuth, was a speedy craft and was quite capable of taking them to Cabin Island and back by evening.

It was a warm, sultry afternoon, and the lads were glad to be out on the cool bay, away from the sweltering heat of the city. It had been an unusually close day, and there had been occasional rumbles of distant thunder.

“We’re going to have a thunderstorm to-night, I’ll bet,” said Biff, as the boat nosed down the bay.

“I don’t think it’ll break before we get back,” said Frank. “It’s a long way off yet.”

The Sleuth drummed along smoothly, and Joe lolled at the wheel. Once they left the narrow end of the bay upon which the city nestled in the glaring sunlight, there was a stiff breeze, vigorous and refreshing.

“Oh, boy!” gloated Chet. “This is the life!”

“It sure is!” the others agreed.

By the time they came within sight of Cabin Island, leaving Bayport far behind, they could see rolling black clouds in the east, and the murmur of thunder had become more continuous.

“We shan’t be able to stay long, I’m afraid,” remarked Frank. “That storm is coming up more quickly than I thought it would.”

“Oh, it’s hours away yet,” scoffed Chet. “You’ll see.”

“Let’s hope so. Anyway, we won’t lose time. We’ll just go up to the cabin and take a quick look around. I don’t want to get caught out in a bad storm. The Sleuth is a good little boat, but the waves run mighty high in the open bay around here.”

Those who followed the adventures of the Hardy boys in “The Mystery of Cabin Island,” are aware that the island, which was owned by Elroy Jefferson, a wealthy antique dealer of Bayport, lay far down Barmet Bay in a little cove. There was a large cabin, built by Mr. Jefferson, fully equipped and furnished, but not occupied by the owner because it had been built for the use of his wife and son. They had died, and the associations of the island had been so painful to him that he had never gone near the place again. However, grateful to the Hardy boys because they had recovered his stolen automobile and because they had solved the mystery of a valuable stamp collection that had been purloined from him, he had turned over the key of the cabin to them with full permission to make use of the place on any of their outings.

They ran the motorboat into the little boathouse and made it secure, then clambered up the familiar path toward the cabin. They had last been on the island in the winter time, when everything was blanketed with snow. Now it was doubly beautiful with its grassy, wooded slopes and its tall trees, among which the cabin stood.

“Make it snappy,” cautioned Frank. “That storm looks worse every minute.”

He opened the cabin door and they stepped inside. The chimney, which had been damaged during a storm the previous winter, had been repaired by some workmen whom Elroy Jefferson had sent to the island, and the place had been thoroughly cleaned. Some new furniture had been installed and on going to the kitchen the boys found a full supply of dishes, kettles, frying pans, cutlery—everything they could possibly need except provisions.

“He must have expected us to come here during the summer!” exclaimed Joe, in delight. “He certainly hasn’t overlooked anything.”

“Mighty good of him, I’ll say!” Chet declared, and his sentiment was echoed by the others. “We have nothing to worry about in the way of kitchen equipment, at any rate. We’ll need only blankets and grub.”

“I think we’ll have a fine outing here.” Frank looked out the window. “Well, we’ve found that we don’t have to worry about the kitchen end of it. Now let’s be going. The storm is right overhead.”

When the boys stepped outside again, all saw that Frank’s desire for haste was well-founded. There were white caps rolling on the bay and the sky was growing black. Even as they started down the path there was a flash of lightning and an ear-splitting crash of thunder. Then followed a gusty shower of rain. The trees were bending before the rising wind.

“We’ll never make it!” shouted Frank. “No use trying to get back to Bayport now.”

“What’ll we do?” asked Chet.

“I guess we’d better go back to the cabin.”

“We haven’t any food, no blankets, no oil in the lights. We’ll probably be stranded here all night.”

“This is a fine lookout,” grumbled Biff. “I wish I hadn’t come.”

As the boys looked out over the bay they could see a sweeping wall of rain approaching above the stormy waters. His companions realized that Frank Hardy was right. They could not hope to brave the perils of that storm by venturing a return to Bayport that night. On the other hand, the prospect of being stranded on the island without food was far from pleasing.

Rain was pouring now. Another lightning flash zigzagged its way through the clouds. Another thunderclap crashed forth.

“Do you think we can reach the village?” shouted Joe.

Frank had almost forgotten about the little village on the mainland not far away which they had visited several times during the winter. Amos Grice, the storekeeper, was a good friend of theirs and his hospitality was preferable to spending a night in a dark cabin, without food or blankets.

“We’ll try it, anyway. If we get into the shelter of the shore I think we can make it all right. Come on fellows!”

The others followed Frank down the steep path to the boathouse, where all clambered into The Sleuth. The engine roared as the boat sped out into the rolling waves, this time Frank taking the wheel.

Smash!

A great wave broke over the bow, drenching the boys to the skin. The full force of the wind caught them as they rounded the point of the island. They were plunging out into a raging waste of waters.

“We’ll never make it!” groaned Chet.

Frank Hardy set his jaw with grim determination as he drove the motorboat into the storm. It was too late to turn back.

The storm had swept up with such speed that Frank realized now that he had underestimated it. The wind was terrific and the waves were high. They battered against the staunch little boat, drenching the boys with flying spray.

Frank headed toward the mainland, but then he saw that he could not hope to find shelter from the wind along the shore. The waves were rolling in and dashing against the rocks. The motorboat would have no chance there. It would be flung hither and thither and battered to pieces.

“Nothing for it but to head right into the wind, I guess,” he shouted, above the howl of the storm.

The other boys were crouching in the bottom of the boat, out of the flying spray. The boat seemed to quiver with successive shocks as it bucked the waves.

The rain was driving into their faces. Through the downpour Frank could not even see the little village toward which they were bound. He wished they had remained on Cabin Island.

The Sleuth, although small, was a strong and well-built craft. The engine throbbed faithfully. None of them dared think of the consequences should the engine fail.

The bow of the craft cut through the rolling waves like a knife. Thunder rolled overhead. The sky was black. The boys could scarcely see the shore. Driving against the wind and the tide, the boat could make little speed, and headway seemed slight.

Nevertheless The Sleuth was edging slowly down the bay, coming ever closer to the little village. Frank peered through the raging storm, hoping to catch sight of the little huddle of houses on the shore.

Lightning flared in the dark sky. Frank held the boat steadily into the wind.

They were all drenched to the skin. Although no one said a word, Frank could see that the others were frightened. As a matter of fact, he was none too confident of the outcome himself.

“It all depends on the engine,” he muttered. “If that fails, we’re done for.”

But the engine had been thoroughly overhauled just the previous week. He was grateful for the foresight that had enabled him and Joe to take this precaution.

Joe crept to the side of his brother.

“Do you think we’ll get there, Frank?” he shouted.

Frank nodded. “It’s dirty weather, but we ought to make it all right.”

Just then he caught sight of the little break in the shoreline that indicated the cove where the village was located. They were still far out, and to reach the village the boat must run diagonal to the waves. This was the hardest test.

The buffeting The Sleuth had previously received was as nothing to what she now suffered. Time and again the boys held their breaths, certain that the boat was about to capsize. Great waves would crash against it, the boat would cant far over on her side, her bow would be buried in the water. Then, like a live thing, The Sleuth would shake herself free, rise above the waves, and go plunging on.

The boys clung to every available hold, fearful of being washed overboard.

Suddenly Joe gave a shout of warning:

“Watch out!”

A great roller was bearing down on them. They ducked, waited——

Crash!

A huge sea of green water engulfed them. For a moment the boat was completely buried beneath the wave. It slipped far over. Frank felt his feet washed from beneath him. He clung to the wheel with all the strength at his command, held his breath through what seemed an eternity of waiting.

Then the motorboat labored free of the wave, slowly righted itself. The water receded. The craft was weighted down by the water that still remained in it, but all the boys were safe. Chet was suffering from a cut across the forehead, where he had been flung against one of the seats; Biff was clutching his wrist, which had been wrenched in his desperate effort to retain his grip on an iron ring; Joe was gasping for breath after his immersion in the water; Frank felt a dull pain in his side, where he had been dashed against the wheel.

More dead than alive, the boys held on. But the village was now in plain view. They had gone through the worst of the storm, and the waves were now hurling the boat in toward the cove.

Frank steered toward a little dock, where the angry waters were dashing themselves angrily against the timbers. He saw a man clad in oilskins running out on the dock, gesturing to them and pointing toward the shore. There was a little boathouse in the cove, and then the man ran from the dock over toward the boathouse, still gesturing.

There was shelter for them. The motorboat would have been dashed to pieces had they tied up to the dock. Frank saw the door of the boathouse open and he drove directly toward it. A great wave caught the craft and it shot forward. A turn of the wheel and he was headed into the narrow opening. He switched off the engine, and then The Sleuth slid gently into the slip.

Tired, exhausted, drenched, the boys clambered out of the boat. The man in oilskins was waiting for them. He seized a rope Frank flung to him and snubbed it around a post.

“Well, now, that was a narrow squeak, if ever I saw one!” he declared in a familiar, nasal voice. “Wust storm we’ve had on this bay for ten years, and you’d be caught in it. You’re mighty lucky, my lads.”

They looked up. They knew that voice well.

“Amos Grice!” exclaimed Frank.

At the sound of his name, the man looked around. Then he recognized the refugees.

“Well, if it ain’t the Hardy boys!” he shouted in welcome. “And Chet and Biff!”

“You certainly did us a good turn that time,” declared Joe.

Amos Grice was soon shaking hands with them, asking a score of questions. How had they come to be out on the bay in the storm? Had they been at Cabin Island? Had they been frightened? How did the boat get half full of water? And so on and so forth. He was a kindly old man, this village storekeeper. He now led the way out of the boathouse.

“Come up to the store,” he said. “Come up and put on some dry clothes. You’re soaked to the hide, all of you. Come up and tell me how it happened.”

“Nothing much to tell, Mr. Grice,” explained Frank. “We were on Cabin Island this afternoon when we saw the storm coming up. We knew there was no chance of getting back to Bayport in time, so we thought we’d run over here, but the storm broke too suddenly for us.”

“It did break sudden,” admitted the storekeeper. “It broke sudden and fierce. I’ve never seen a worse storm in ten years.”

He took them up to the store, and in a warm kitchen at the back he bade them dry themselves by the fire while he hustled about and procured dry clothing. Amos Grice was a bachelor, and while his living quarters were crude, they were neat and comfortable. He was genuinely delighted to see the boys, and he soon busied himself at the stove preparing supper.

After a hearty meal the lads were feeling more comfortable and their hazardous adventure on the bay did not seem quite so perilous as they looked back on it.

“I guess we won’t be able to get back to the city to-night,” said Frank regretfully.

Amos Grice snorted.

“I wouldn’t hear of it!” he declared. “Couldn’t think of it! Just suicide to try it. No, sir, you lads have got to spend the night with me, and glad I am to have you. It’s seldom enough I have company here.”

“As long as you have room for us——”

“Of course I have room for you. There’s two big beds in the spare room, and you’re more than welcome.”

A bell occasionally tinkled out in the store, and Amos Grice bustled away to wait on a customer. However, there were few people in the little village and the night was so wild and stormy that nearly everyone was staying indoors, so the interruptions were few.

They chatted with the old man all that evening, sitting by the fire, and eventually he showed them to a big room where the beds were already made.

“Now,” he said, “sleep as long as you wish and I’ll have some breakfast for you in the morning. No doubt your parents is worryin’ about you, and I’d phone ’em if I could, to let ’em know you’re all safe and sound. But the telephone wires is down somewhere along the line. They’ll likely be fixed by morning.”

“Dad and mother will certainly be worrying about us,” said Joe.

“Can’t be helped,” returned Amos philosophically. “They’ll feel all the better when they know you’re safe.”

The boys were tired and they fell asleep quickly. In the morning when they awakened the sun was shining in the window. The storm was over. Out in the kitchen a fire crackled in the stove and they could hear Amos Grice moving about. There was a savory aroma of bacon and eggs and coffee.

“He’s certainly a good scout!” declared Chet, as they dressed.

“Can’t be beat,” agreed Biff.

When the boys were washed and dressed, they went out into the kitchen.

“Sleep well?” inquired Amos.

“You bet!”

“That’s good. Breakfast is ready. Pull your chairs up to the table and get on the outside of some bacon and eggs. There’s plenty, so don’t be afeared to ask for second helpin’s.”

“Is the telephone working, Mr. Grice?” asked Frank. “I’d like to call them up at home if I can.”

“Yep, the phone is workin’ again,” the storekeeper assured them. “I know, because I was callin’ the operator this morning. Big doin’s in Bayport last night.”

“What was that?” asked Joe, interested.

“Big robbery at the airport. One of them airplanes was robbed of a lot of mail worth more’n twenty thousand dollars, so the telephone operator was tellin’ me.”

The Hardy boys looked at one another in amazement. A second robbery at the airport! Impulsively, Frank exclaimed:

“Ducroy again!”

“What’s that?” demanded the storekeeper abruptly, in response to Frank Hardy’s inadvertent exclamation.

“Nothing,” answered Frank. “I was surprised—that’s all. You see, there was a robbery at the airport only a day or so ago.”

“Another one, eh? Well, they oughta watch that place more careful, that’s all I can say. People won’t be sendin’ their letters by airplane if they think they’re goin’ to be stolen all the time.”

“That’s a case for you fellows,” said Biff.

Neither Biff nor Chet were aware of the depth of the Hardy boy’s interest in the airport robberies.

“Did the operator tell you anything more about that affair, Mr. Grice?” asked Frank, after a pause.

“Nothin’ more than what I’ve told you. She just said there was a big robbery and twenty thousand dollars’ worth of mail had been stolen last night.”

Joe went to the telephone. After some delay he managed to get the Hardy home in Bayport on the wire. His mother’s voice answered.

“Hello, Mother! This is Joe talking.”

Her voice had an unmistakable note of relief as she answered:

“Joe! Oh, I’m so glad to hear your voice again. Your father and I have been greatly worried about you. Where are you? What happened? Why didn’t you come home last night?”

“Don’t worry, Mother. We were caught in the storm and we couldn’t get back. We’re quite safe. We’re at Mr. Grice’s place, down below Cabin Island.”

“Well, I’m glad to hear that. When are you coming home?”

“We’re coming back to-day. Would you mind telephoning to Mrs. Morton and Mrs. Hooper? Tell them that Chet and Biff are with us and that they’re all right too.”

“I’ll do that, Joe. Just a minute. Your father wants to speak to you.”

Joe waited a moment. Then he heard his father’s voice.

“Hello, Son. You’ve given us a pretty bad scare.”

“We’re sorry, Dad, but we got caught in the storm.”

“Let me in on this, Joe,” begged Frank; and when Joe had put the telephone in his brother’s hand the older Hardy boy continued: “Hello, Dad! Worried you and mother, did we? Sorry. But we’re all right. Will tell you about it when we get back.”

“Well, I’m glad you’re all right. Now listen. I want you and Joe to come home at once.”

“Sure. We are just going to leave.”

“Come back to Bayport at once. Something has happened.”

“What’s wrong, Dad?”

“I’ll tell you when you reach here. But don’t lose any time.”

“Is it about the airport robbery?” asked Frank.

“How did you know there was a robbery at the airport?” demanded his father in an anxious tone.

“We heard it this morning through Mr. Grice.”

“Well, it’s connected with the robbery, but it’s a little worse than that. Come right home, mind now.”

“All right, Dad. We’ll leave right away.”

Frank hung up the receiver and turned to the others. He was puzzled.

“I guess we can’t hang around here this morning. Dad wants us back right away. He seems awfully anxious.”

“Anything wrong at home?” asked Joe quickly. “Mother didn’t say so.”

“Everything’s all right there, I guess. But Dad has something on his mind. He said he’d explain it when we got home.”

“Shucks!” grumbled Amos Grice. “And I counted on takin’ you lads out fishin’ this morning.”

“I guess we’ll have to call it off, Mr. Grice. Some other time, perhaps.”

Chet Morton sighed and ate another slice of bacon.

“I guess we’ll all catch it when we get home. Was your Dad sore, Frank?”

“No, he didn’t seem angry. I can’t imagine what’s wrong. Well, I guess we’ll have to bail out the boat right after breakfast and start for home.”

After they had eaten, Amos Grice helped them bail out the motorboat. It had stood the storm well, in spite of the terrific battering it had received. The old storekeeper was disappointed because his young guests could not remain with him longer, and when they thanked him heartily for his kindness he waved their gratitude aside.

“A pleasure,” he told them. “I’m always glad to see you. Any time you’re down this way, be sure and drop in.”

“We’ll pick better weather next time, Mr. Grice,” laughed Chet.

“In fair weather or foul, you’re always welcome.”

They got into the boat and started off. The storekeeper stood on the dock and waved to them as they departed. Then he turned and walked slowly up toward his store.

Joe came up and sat beside Frank, who was at the wheel.

“What do you think has happened, Frank?”

“I can’t imagine. It has something to do with the robbery last night, I’m sure.”

“But why should dad want us back right away?” Joe insisted.

Frank shrugged. “It beats me. Perhaps he has some work for us to do, helping him trace the thieves.”

“Maybe that’s it. I sure hope so.”

Frank was silent for a while. Then he said:

“I wonder if Giles Ducroy and his friends will have an alibi this time.”

“It will have to be a mighty good one. Just think of it! Two mail thefts in a row. Whoever did last night’s job must know the run of the airport pretty well.”

“Whoever committed the first robbery knew the lay of the land too. If we solve the first one we’ve solved them both.”

“We?” said Joe. “I don’t think we’ll have much chance to solve it. This is dad’s case. I’ll bet it won’t take him very long to clear it up, either.”

But, with all their conjectures, the Hardy boys had no suspicion of the real reason for their summons back to Bayport. Had they known what had caused that note of urgency and anxiety in their father’s voice, they would have been dumbfounded. A stunning surprise awaited them.

They passed Cabin Island and headed out of the cove into the open bay. The water was still rough from yesterday’s storm, but there was little wind. After a while the city came in sight far in the distance, shining in the sunlight, beneath a pall of smoke from the factory chimneys.

It was a few minutes before twelve o’clock when the boys finally arrived at Bayport and ran The Sleuth into the boathouse. To their surprise they saw that a man was lounging in the doorway. He was a big man, with a fat, stolid face, and he was chewing at an unlighted cigar, his thumbs in his vest pockets.

“Good mornin’, boys,” he rumbled.

They recognized him as Detective Smuff, of the Bayport police department, a worthy if unintelligent officer. Frank could not imagine why Smuff should be in the boathouse, apparently waiting for them, but he grinned amiably at the detective.

“Hello, Mr. Smuff! It is an unexpected surprise to find you here.”

Smuff nodded portentously. “It is?” he asked.

“Last person in the world we ever thought would come down to welcome us,” declared Chet. “I tell you, Mr. Smuff, we sure appreciate this. It isn’t often we have a reception committee on the job when we come back from a little outing.”

“Well,” said Smuff, “I’m on the job this time.” He turned to the Hardy boys. “I’ve been sent down here to give you a message as soon as you got in,” he informed them.

“A message!” exclaimed Joe. “Who from?”

“The chief. He wants to see you down at headquarters.”

The Hardy boys stared at the detective in amazement.

“The chief? Wants to see us?” ejaculated Frank.

“Yep.”

“What about?” demanded Joe.

Smuff looked very mysterious. “You’ll know all about it when you get there,” he said.

“You’re going to be pinched for staying out all night,” laughed Chet. “That’s a fine thing to do, Smuff—pinch our chums the minute we get back to town. A fine reception committee you are!”

“I didn’t say anybody was pinched,” returned Smuff cautiously.

“Well,” said Frank, “this is a surprise! Won’t you tell us what it’s all about?”

Smuff shook his head. “My orders,” he explained, “was to come down here and wait for you and to tell you to come up and see the chief right away.”

“Why not let us wait until after lunch? We want to go home and eat and change our clothes.”

“Orders is orders,” insisted Smuff firmly. “The chief wants to see you right away.”

“All right,” sighed Joe. “I suppose we’ll have to go. But I wish I knew what it was all about.”

“Me, too,” rejoined his brother.

Biff, who had been tying up the boat, came forward.

“He probably wants to fire Smuff, here, and give you jobs on the detective force,” he suggested, with a grin.

Smuff glowered. “My job is good for a long time yet,” he observed pompously.

“Come on,” said Frank. “There’s no use standing here arguing about it. We’ll go with you, Smuff.”

“I have my car right here at the door,” said the detective.

“That’s service,” chirped Chet. “Biff and I will run along home. Our parents will be worrying themselves sick if we don’t show up. So long, fellows! If Smuff claps you into a cell, we’ll come and bail you out!”

Chet and Biff hastened off down the street while the Hardy boys clambered into Smuff’s car. The detective wedged himself in behind the wheel and they drove the few short blocks to police headquarters.

Here they were ushered into the private office of Chief Collig himself, a fussy little man with a vast sense of dignity. The chief was sitting at a huge desk, scanning a large number of photographs of criminals, but he stacked these to one side as Detective Smuff brought the boys in.

“Good day, Chief,” said Frank easily. “Detective Smuff, here, said you wanted to see us.”

“I did,” snapped Chief Collig.

“Well, here we are.”

“You’re wanted,” said Collig briefly.

“Wanted?” asked Frank. “What do you mean?”

“You’re wanted by the postal authorities. I have orders to place you under arrest.”

The lads were so astonished that they could scarcely speak. Under arrest? This was the last thing either had expected.

“What for?” gasped Joe. “What’s the idea?”

“You know about the airport robbery, don’t you?” demanded Chief Collig.

“Yes, we know about it. But——”

“Well, they say you did it. I have orders to arrest you both.”