When the Hardy boys arrived at Riverside Field they looked in vain for Giles Ducroy and his friends. But the trio were not in sight, and there was but one airplane on the flying field. It was a small two-seater.

“It can’t be their plane,” said Frank. “Ollie Jacobs said it would hold four or five men.”

“Perhaps they haven’t arrived yet,” Joe suggested.

“They had only thirty miles to go. They should have been here long ago.”

“We can go up to one of the hangars and ask what planes have come in.”

Frank was dubious. “If Ducroy or any of the others are hanging around, we’ll be spotted. Our game is to keep out of sight.”

They sauntered over to the solitary little airplane in the middle of the flying field. A mechanic in grimy overalls was busy tinkering at the understructure of the machine.

“Is this the only plane here?” asked Frank politely.

The mechanic looked up. “It’s the only one out on the field,” he answered. “If you can see any more, let me know.” He grinned, and then waved toward one of the hangars. “An old crate just flew in a few minutes ago.”

“Where from?”

“How should I know? Airplanes, unless they’re on the mail run, aren’t like trains. Looked to me like a privately owned machine.”

The Hardy boys glanced significantly at one another. They had no doubt that this was Ducroy’s plane.

“Is the pilot in there now?”

The mechanic nodded. “Him and two other guys.”

Frank and Joe thanked their informant and made a wide detour across the flying field so as to approach the hangar at the far side. They had no desire to meet Giles Ducroy and his friends just now. They came around to the rear of the hangar without being observed and while they were looking about for a means of entrance other than by the front, Joe discovered a small door at the side.

He tried the door. It was unlocked. Joe edged it open and peeped in.

There was the plane, at rest in the hangar, and standing beside it were Giles Ducroy, Newt Pipps, and Ollie Jacobs. They were talking in low tones. Even as the boys watched they saw Ollie Jacobs move away from the others.

“It won’t take long,” he said. “I’ll do some telephoning and find out all I can.”

“Make sure of the date!” advised Ducroy.

Ollie Jacobs left the hangar. For a moment the Hardy boys were panic-stricken at the thought that he might look back and see them pressed against the side of the building, but Jacobs strode away without once glancing behind.

“I wish we could learn something definite,” whispered Joe. “This thing of following them around is beginning to get on my nerves. They are bound to catch sight of us, sooner or later.”

“We certainly can’t follow them around like this,” agreed Frank. “If they don’t see us, we’re liable to lose them anyway. If we can only find out what game they’re up to!”

They peeped through the opening in the door again. But Ducroy and Newt Pipps had withdrawn a little way to one side and were talking in undertones, their words inaudible.

In about ten minutes, Ollie Jacobs returned. He hastened into the hangar, and Ducroy looked at him expectantly.

“Well,” the boys heard Ducroy saying, “did you learn anything?”

“I sure did,” returned Ollie Jacobs. “It’s all settled. And we don’t have to wait as long as we thought we might.”

“That’s good,” declared Ducroy, rubbing his hands together with satisfaction. “What did he say?”

“The shipment will come on the night of the twenty-eighth.”

“As soon as that!” exclaimed Newt Pipps.

“We’ll be ready for it,” snapped Ducroy. “We’ll force him down not far from here.”

“It will be at night, eh?” said Pipps.

“Of course. All the better, too. I’d think twice before I’d try this trick in daylight.”

“I guess you’re right,” admitted Newt feebly. “Although I don’t like the idea of it at any time. You’re sure we’ll have only one man to handle?”

“Only one man. And there are three of us. We’re not taking a chance of failing.”

“How are we going to force him down?” asked Ollie Jacobs.

“Leave that to me,” answered Ducroy confidently. “There’s more than one way of doing that.”

“Let’s go and eat,” Newt suggested. “I’m half starved.”

“That’s a good idea,” Ollie agreed. “There’s a little restaurant near here. What do you figure on doing, Giles? Do you think we should stay right here at the airport until the twenty-eighth?”

“No,” said Ducroy firmly. “I don’t. The authorities are apt to find us if we stay in one place for any length of time. We’ll have to keep going. We’ll move around from one place to the other until the time comes. We can’t afford to be nabbed now. And after the twenty-eighth we’ll clear out for good.”

The three men moved up toward the front of the hangar, left the building, and went on across the flying field toward a small restaurant in the distance. There was a little lunch counter near by but the men ignored it for the more pretentious eating place.

Frank and Joe Hardy slipped quickly into the hangar through the side door. Instead of clearing up the mystery that puzzled them, the conversation they had just overheard confused them more than ever. That some criminal coup was in the wind for the night of the twenty-eighth was no longer in doubt, but what it was and where it was to take place still remained unrevealed.

“I don’t understand what’s happening,” said Frank, as he looked at the airplane in the hangar; “but I know we’ve got to be on hand if we can possibly manage it.”

“How can we be on hand if they’re going to keep flying from place to place for the next two days?” asked Joe.

“We’ve got to keep track of them somehow.” Frank moved about, inspecting the airplane. “I’d just like to reserve a back seat in this plane for the next forty-eight hours.”

“That idea isn’t as silly as it sounds!” declared Joe. “Why can’t we?”

Frank laughed. “How can we? They’d simply kick us out, for we’d certainly be seen.”

“Not if we went about it right.” Joe was excited as the possibilities of his idea became more apparent. “Why can’t we be stowaways? Don’t you remember the time we hid ourselves in the back of the automobile when we solved the Shore Road mystery? We could hide here too. I’ve heard of airplane stowaways before.”

“It’s a nervy idea,” said Frank. “I wonder where we could hide?” He moved down toward the rear of the plane. Suddenly he halted. “Just what we want, Joe! Here’s an opening.” He thrust the sliding door aside and looked into the dark interior. The tail of the plane was hollow and he could see a substantial hiding place. Considerable space was available for freight or baggage and, inasmuch as Ducroy and his friends were travelling light, there was plenty of room for the two boys.

“How about it?” asked Joe.

“I’m game. But how about food? We’ll be in there for quite a while, you know.”

“We’ll get sandwiches and water. Some blankets too, for that matter. We’ll simply stow away in there and make ourselves comfortable. Then, if anything happens, we’ll be right on hand.”

“We’ll be right on hand too if the plane crashes,” Frank reminded his brother. “Perhaps we’ll weight it down too much.”

“I don’t think so. This plane is designed to carry baggage, and if that space is empty, we’ll never be noticed. I think we can get away with it, provided we have any luck at all. It’s easily our best chance of keeping in touch with Ducroy and his gang. If they’re going to be flying around the country trying to dodge the authorities, we shan’t have much chance of keeping our eyes on them in our car.”

“That’s right, too.” Frank made up his mind. “I’m with you, Joe. And now’s our chance. Let’s get water and sandwiches and get into the plane while we have time.”

It seemed a mad scheme, but the brothers knew the importance of keeping close to Ducroy and his friends. Some crime had been planned for the night of the twenty-eighth, and the Hardy boys knew they must not lose track of their quarry for a moment. It would have been obviously impossible to follow the meanderings of the airplane from the ground.

They hastened over to the little lunch counter and laid in a stock of provisions. Several bottles of milk, a huge bottle of water, some cake and a stock of sandwiches constituted their supplies. At the lunch counter they spied two heavy automobile robes, and as it was too late to return to their own roadster, they bought the robes and entrusted the lunch counter man with the duty of driving their own car to a garage for safe-keeping. This he promised to do. Doubtless he wondered the reason for the boys’ purchases, but he was a man who believed in minding his own business and he exhibited no surprise or curiosity.

Frank and Joe hurried back into the hangar. They tossed the robes into their hiding place in the plane, arranged them comfortably, then stowed away the food and water.

“All set?” asked Frank finally.

“All set.”

Joe began to scramble into the plane.

“Just in time, too,” said the brother.

“Why?” asked Joe, in a muffled voice, as he crouched back on one of the automobile robes.

“Giles Ducroy and his friends are coming back across the flying field.”

Frank got into the plane. Quickly he closed the door. The two boys waited apprehensively. Had their presence been detected? Would the lunch-counter man mention having seen them? Would Ducroy glance into the baggage compartment before leaving?

But nothing happened. They heard the three men come into the hangar. They heard them moving about, evidently preparing for departure. Finally, they heard Ducroy’s voice:

“Get in. We’re away again.”

The plane was trundled out on the field. A moment later the motor roared, the machine bumped its way across the field, then the bumping motion ceased and the Hardy boys knew that they were in the air.

Although their flight as stowaways in the airplane was one of the most dangerous and perilous adventures that had ever befallen the Hardy boys, it was at the same time the most monotonous.

Back there in the darkness they could see nothing and they could hear very little except the roar of the engine. They were not uncomfortable and they did not suffer from lack of air, but it was not a pleasant sensation to reflect that they were high above the earth, wholly at the mercy of the rascals up in the front of the plane.

The plane dipped and rose, banked and turned. There were racks, presumably for the accommodation of baggage, to which the lads clung, so that at no time were they thrown off balance.

“If we get to tossing around in here, they’ll notice something wrong,” said Frank.

Their weight was evenly distributed and presumably Giles Ducroy did not see that his plane was somewhat tail-heavy. If he did, it is probable that he blamed the airplane itself, for it was strange to him.

After about an hour in the air, the boys were obliged to seize the racks, for the nose of the machine tilted downward and they were almost flung ahead as the plane descended. Finally there was a slight shock, and the plane bumped its way over a field. They could hear men’s voices, then the engine was shut off. They judged that Ducroy and the others were clambering out.

“Now,” they heard Ducroy saying, “I guess it’s safe enough for me to go and telephone.”

“Who are you going to telephone to?” asked Newt Pipps.

“I’m going to call up Jed. He’s at the Bayport airport. I’ll tell him to be ready for the night of the twenty-eighth so he can call us up when the time comes.”

“I don’t like the idea of having so many outsiders in on this,” Newt grumbled. “It means we’ll have to split the loot too many different ways.”

“Outsider!” snapped Ducroy. “Jed isn’t an outsider. How could we get along without him? We’re going to make a killing before long, and a lot of the credit will be due to him.”

“You’re right,” agreed Ollie Jacobs. “Shut up, Newt. We can’t get along without Jed. If you were half as much help as him we’d get along fine. You’re always kicking about something.”

This reprimand silenced Newt Pipps for the time being. The Hardy boys, listening, heard the three men move away.

When the footsteps and voices could no longer be heard, Joe heard Frank’s voice from the darkness:

“I wish I knew how long they’re going to be away. I’d like to get out of here and stretch my legs.”

“So would I. It’s mighty cramped in here. But if they’ve just gone to telephone I don’t think we should take the chance.”

Frank opened the door in the side of the plane and looked out.

“I can see them now. They’re walking across the field toward one of the hangars.”

“Where are we?” asked Joe.

Frank shook his head. “I don’t know. There seems to be a fair-sized town close by, but I’ve never seen the place before. I can see factory chimneys and church steeples.”

“Let’s have something to eat.”

Joe opened their package of sandwiches, a bottle of milk, and the bottle of water. Each ate of the frugal meal with enthusiasm, for they were hungry by now. When they had eaten they felt better, and in spite of the discomfort of their quarters they began to enjoy the novelty of the adventure.

“If only Chet and the other fellows could see us now!” said Joe.

“They’d be green with envy.”

“I’m not sure our position’s enviable.”

“We’re not out of the woods yet, by any means,” agreed Frank. “Ducroy and the others are apt to find us at any time. We’ll have to sit mighty tight.”

“If only we knew what they’re up to! It must have something to do with the Bayport air field. They’ve evidently got a confederate there, keeping in touch with him by telephone.”

“I think,” said Frank, “I’ll get out and stretch my legs a bit.” He opened the door a little wider and was just about to scramble out when he gave an exclamation and hastily drew back again, closing the door.

“What’s the matter?” whispered Joe.

“They’re coming back!”

Both boys were silent. They could hear voices, gradually growing louder. Frank wondered if he had been seen. Ducroy, Newt Pipps and Ollie Jacobs had not been more than a hundred yards away when he opened the door.

“There’s no room in the hangars,” Ducroy was saying, “but we’ll stay here overnight just the same. There’s a hotel not far from the field. Then, in the morning, we’ll get under way again.”

“What time?” asked Jacobs.

“About eight o’clock. We’ll have breakfast and then start again.”

“I don’t see why we can’t stay right here until we’re ready for the big job,” grumbled Newt Pipps. “What good does it do flying around from place to place?”

“If the police pick us up you’ll wish we had kept going,” declared Ducroy. “We can’t afford to be nabbed now. We’ve simply got to keep clear of the cops until the night of the twenty-eighth. After that we’ll scatter, and each take his own chance. The police will be looking for us hot enough then.”

“They sure will,” agreed Ollie. “Well, let’s go on over to the hotel. The plane is all right here, ain’t it?”

“Sure. It’s safe enough overnight. We’ll come back after breakfast and get under way again.”

The men moved off. After a while, when Frank Hardy peeped out again, he saw them going through a gate on the far side of the flying field, evidently heading toward the town. He breathed a sigh of relief.

“That’s a bit of luck,” he said to Joe. “We don’t have to stay cooped up in here all night. As long as we get back here well before they show up in the morning everything will be fine.”

“Where can we stay? We can’t go to the hotel. I don’t think it’s even wise to go into the town at all. If they ever catch sight of us it will spoil everything.”

Frank scrambled out of the plane. He walked about, enjoying the feel of solid ground beneath his feet again. Joe followed, and immediately turned a handspring to express his delight.

“Makes you feel good, doesn’t it?” said his brother, grinning.

“I’ll tell the world it does, Frank! Gee, I feel as cramped as a sardine in a tin.”

“So do I.” Frank stretched himself. “Say, we were mighty lucky they didn’t discover us.”

“Right you are. If they had—well, there is no telling what they would have done.”

“They might have killed us, Joe.”

“Oh, maybe not as bad as that. But they might have tied us up in the woods and left us there.”

“They are a bad crowd.”

“I agree with you.”

The brothers took a look at their surroundings from every side.

“We’d better move away from the plane,” advised Frank. “Some of the mechanics at the hangars may see us and tell Ducroy. I think our best bet is to go to that farmhouse on the other side of the field.”

“Perhaps we can use the telephone there, if they have one.”

In the fading light, the boys crossed the field, climbed over the fence and made their way toward the farmhouse. As they entered the barnyard, a collie dog ran toward them, barking. He was a friendly animal, however, and as he approached he wagged his tail and fawned on them. A stout, cheery-looking man was standing in the doorway of the house.

“Hello, boys,” he shouted. “What can I do for you?”

“Have you a telephone?” asked Frank.

The farmer nodded. “You’re welcome to use it,” he said, then added: “As long as you pay the charges.”

“We’ll do that all right.”

The farmer led them into the house and indicated the telephone in the hall.

“Talk away,” he said. “I saw you coming over from the flying field,” he remarked shrewdly. “Why didn’t you use the telephone there?”

“Private reasons,” replied Joe.

The farmer did not move away while Frank put in a call for Chief Collig at Bayport. At mention of the chief’s name he seemed interested, and when Frank finally got the chief on the wire, he listened with all his ears.

“Chief Collig?” asked Frank. “This is Frank Hardy speaking.—No, we haven’t jumped bail.—What’s that?—We’ll be back in good time.—The reason I’m calling you is to warn you to keep a good watch on the airport on the night of the twenty-eighth.—I can’t tell you why.—There is going to be some trouble.—I don’t know anything more about it than that.—It will be worth your while to make use of this warning.—Where am I speaking from? I can’t tell you. And listen, Chief, will you call up my mother by telephone and let her know that I called you and that Joe and I are all right?—Thanks. Good-bye.”

When Frank rang off, he saw that the farmer was regarding him curiously.

“Looks as if you boys are smarter than you seem,” he remarked. “What are you? Detectives?”

“I suppose you might call us that,” admitted Frank. “But we’d be obliged if you would say nothing to anyone at the airport about us.”

“You can trust me,” returned the man. “I can keep my mouth shut. Where are you staying to-night?”

“We don’t know yet,” said Joe.

“If you’d like to stay here, we have a spare room, and you’re welcome to it,” the farmer volunteered.

“That’s mighty good of you. We were just wondering where we would find a place to sleep. We have to be up and out by seven o’clock, though.”

“I get up at five, myself,” laughed the farmer. “Come on into the kitchen and I’ll have my wife fix up something to eat. You’re more than welcome to stay with us overnight. I’m dyin’ to know what you lads are up to, but I guess I’d better not ask too many questions.”

“You’ll read all about it in the papers,” laughed Frank, “if everything works out the way we want it to.”

The next day was the twenty-seventh and the Hardy boys knew that they had another day to put in before Ducroy and his friends would be ready for the mysterious coup for which they had laid so many plans.

Frank and Joe were up early, and after a substantial breakfast at the farmhouse they said good-bye to the good-natured farmer and his wife, then hastened across the fields toward the airport again. There were a few signs of life about the hangars; some mechanics were busy at a plane out in the field; a new machine was preparing for a take-off. But the Ducroy plane was deserted and the lads saw that they were in good time to conceal themselves again.

With a fresh supply of water and sandwiches which they had obtained at the farmhouse, they went casually over to the plane, looked around to see that they were not observed, and then, when the coast seemed clear, they slipped quietly into their hiding place.

“Another day ahead of us!” said Frank. “I wish this was the morning of the twenty-eighth instead of only the twenty-seventh.”

“We’ll get through somehow. I hope they don’t keep flying around all day. It gets mighty monotonous being cooped up like this in here.”

Frank made himself more comfortable on his automobile robe.

“We could be worse off. We have lots to eat and drink, and we don’t have to worry about steering the plane.”

“I like to see where I’m going,” said Joe dubiously.

“As long as Ducroy stays sober he isn’t a bad pilot,” returned Frank. “I guess the other pair will see that he’s fit to take the controls before they’ll fly with him. Their necks are just as precious to them as ours are to us.”

“Guess we’d better keep quiet now. They may be along any minute.”

The lads lapsed into silence. In about half an hour they could hear voices and then came footsteps.

“Just a short jump to-day,” they heard Ducroy saying. “Just a short jump, and then we’ll lay low until to-morrow night.”

“Where are we going?” asked Newt Pipps quickly.

“You’ll know when we get there.”

“I wish we could have stayed here,” insisted Newt. “I could have stood another two hours’ sleep easily.”

“If we stick around here we’ll be liable to find ourselves sleeping in jail,” said Ollie Jacobs. “I got the scare of my life when that cop came up and spoke to us.”

“I thought we were sunk,” admitted Ducroy. “He had been eying us for quite a while and I was getting nervous. I was sure he had spotted us.”

“You stood him off all right. That was pretty good, telling him we were stunt pilots on our way to Hollywood. He swallowed it, hook, line, and sinker.”

“Just the same,” observed Ducroy, “you see how easy it is to run into trouble. If that cop had been a little wiser we might have been in the jug right now. And if he starts talking to some other cop and describes us, we may find ourselves in trouble yet. So the sooner we get out of here the better.”

This sentiment seemed to find favor with the others, for there was considerable bustling around as they prepared to take off again. In due time the propeller began to whirl, the engine burst into a roar, the plane quivered. The boys heard a shout from Ducroy, and then the airplane moved slowly off across the field.

It bumped and rocked along, its progress becoming smoother as it gathered speed; then it left the ground, the body of the plane tilted a little as it began to climb. After a while it banked, circled about, then straightened in swift flight.

It was hot and stuffy back in the compartment where the Hardy boys had hidden themselves, but they comforted themselves by remembering that Ducroy had said this was to be only a short jump. After that, the rascals evidently planned to lie in hiding until the night of the twenty-eighth.

The plane drummed along at a good speed for some time. Then the nose dipped so suddenly that the lads were flung forward. Their weight being thrown ahead, the tail was suddenly lighter and the plane went into a sudden dive. They heard a yell of alarm from one of the men in the forward part of the machine, but the plane straightened out as swiftly as it had lost balance. Frank and Joe had been frightened for the moment but they soon regained their accustomed positions again and clung tightly to the racks while the plane descended in sweeping circles.

It went into a long glide finally, then the wheels bumped against the ground. It rose into the air, bumped again, then taxied across a field until it gradually came to a stop. The motor was suddenly shut off.

“What happened?” they heard Newt Pipps shout in alarm.

“Lost control there for a minute,” Ducroy answered. “She went into a dive a lot faster than I had figured on.”

“I thought we were going to crash,” declared Newt shakily.

“Not with me at the controls,” boasted Ducroy. “I don’t know what went wrong, but it didn’t take me long to straighten her out.”

“It was just as if we had some baggage in the back and it shifted forward,” said Ollie Jacobs.

The Hardy boys were breathless with apprehension. Perhaps Ducroy would be tempted to investigate!

“Well, there’s no baggage,” insisted Ducroy. “It’s just the plane. I’m not quite used to it yet.”

“I’ll be glad when this business is over,” said Newt. “I don’t like this flying business, anyway. Solid earth is good enough for me any day. When this job is over and I get my share of the money it’ll be a long time before anyone tempts me into an airplane again.”

“Where are we now?” asked Ollie. “This isn’t a flying field.”

“It’s better,” returned Ducroy. “This is an abandoned farm. We’re quite safe here. If anyone comes to investigate, we’ll just say we ran out of gas and have to wait here for a while until we get a fresh supply.”

“We’ll stay here until to-morrow night, then?” asked Newt.

“There’s a little village about a mile away. We can go there and stay overnight and loaf around to-morrow. It’s a lot better than hanging around a flying field where people are apt to ask questions.”

“This suits me all right,” said Ollie Jacobs. “I didn’t like the idea of hopping around from place to place the way we were doing. The plane is safe enough here, I guess.”

“A few farmers may drop around to have a look at it, but I don’t think there’s any danger of anyone stealing it,” said Ducroy. “We might as well go on into the village.”

“I’m hungry,” declared Newt. “This flying gives me an appetite. Let’s go and get something to eat.”

The Hardy boys listened as the voices diminished in the distance. When they could no longer hear the trio, Frank opened the side door and peeped out. He could see Ducroy and the others climbing over a fence at the other side of a wide field. The men went out to the road and then trudged on toward a little village lying in a hollow about a mile away.

The boys breathed sighs of relief as they scrambled out.

“This is luck!” said Frank. “No more flying until to-morrow night.”

“I hope we don’t have to stay inside the plane until then. Those fellows are apt to come back at any minute.”

“I don’t think so. You heard what they said. They intend to stay here until to-morrow night. As long as we show up here in good time to hide ourselves before they leave, we’re all right.” Frank strode up and down the field, taking the kinks out of his legs. “Let’s take our sandwiches and go over to that abandoned farmhouse. We can stay there quite comfortably until it’s time to leave.”

Joe agreed. “We’ll have to keep an eye on the road. We can’t afford to let them see us getting into the plane and we can’t afford to let them start without us.”

“We’ve stayed with them so far and we’ve got to stay with them to the finish,” declared Frank. “I only wish we knew where this business is going to end.”

They took their package of food from the plane and went across the field toward the farmhouse. It had been abandoned for some years and was in a bad state of repair, but it sufficed for their purpose. The boys spent the greater part of the day exploring the place, and toward mid-afternoon Frank suggested that they might as well sleep there that night. They went back to the plane, which had been undisturbed, and removed the automobile robes, bringing them back to the house.

“We’ll have to sleep on the floor to-night,” laughed Frank.

“I don’t care where we sleep, as long as we get these rascals where we want them.”

They found a spring down in the orchard, and the cold spring water served to make more palatable the sandwiches the farmer’s wife had made for them that morning. Toward evening they went into one of the upper rooms of the house and looked out over the field toward the plane. There they saw three figures walking across the field.

“I hope they’re not going to start off again,” said Joe, in alarm.

“They’ve probably just come back to see if the plane is all right.”

The three men were Giles Ducroy and his companions, and their errand was evidently as Frank had suggested. Ducroy went over the plane very carefully. Then he went toward the back and suddenly pulled open the door in the side. The boys saw him peer into the interior of the plane.

“Boy, isn’t it lucky we didn’t stay there!” exclaimed Joe.

“I hope he doesn’t find that water bottle. We left it there. Remember?”

But Ducroy’s inspection was brief. He drew back, closed the door again and turned to the others with an expressive gesture. Frank and Joe realized that he had merely made the inspection to satisfy the others that there was no baggage in the plane. Evidently the water bottle had gone unnoticed.

The trio stayed only a few minutes, then went back across the field again toward the village.

“That’s that!” said Frank. “We’re all right now until to-morrow night. We’ll go over some time in the afternoon, hide ourselves and then wait for things to happen.”

The boys stayed in the empty farmhouse that night, and they slept soundly in the automobile robes, despite the hardness of the floor. The gray light of dawn was just shining through the window when Frank heard a sound that awakened him with a start.

It was the throbbing roar of an airplane engine!

He got up and scrambled over to the window. When he looked out he was just in time to see a figure clambering into the cockpit of the plane out in the field. Then the machine began to move across the pasture; its speed increased; it rose from the ground, skimmed above the fence, rose higher and higher into the air and then headed far off beyond the village.

Joe, in the meantime, had been aroused by the noise of the engine, and he too witnessed the airplane’s flight.

Disheartened and discouraged, the boys looked glumly at one another.

“I guess that means we’re licked,” said Joe, at last.

After all their precautions, the sailing away of the airplane without them was a bitter pill to swallow. The Hardy boys had been so confident that the men would remain in this place until the night of the twenty-eighth that this early morning flight took them completely by surprise.

“We’ve lost them now,” said Frank. “We don’t know where they’re going or where this hold-up, or whatever it is, is going to take place. And we don’t even know where we are ourselves.”

“It’s tough luck. After all the trouble we went to!”

“I guess the only thing we can do now is go back to Bayport and do our best to warn the post office authorities. I have a pretty good hunch that the gang are planning another air mail robbery. Why else would they use a plane?”

“Not much use staying here,” agreed Joe. “They certainly stole a march on us that time.”

They got dressed and left the empty house. Neither said very much, for they were discouraged beyond measure. All their discomfort of the past two days seemed to have gone for nothing. They realized that the defeat was not their fault, because they could not anticipate that Ducroy and his cronies would leave that morning when they had definitely planned to remain in the vicinity all day; but there remained the unescapable fact that the quarry had eluded them.

“Perhaps the police in the village recognized them and they had to clear out,” suggested Joe.

“I guess that’s the reason. I can’t think of any other.”

They trudged down the lane that led out toward the village road. Their immediate plan was to reach the village, find out where they were, and then return to Bayport as soon as possible.

“There’s just a slim chance we may be able to catch them yet if we tell the post office authorities all we know,” Frank pointed out. “But we haven’t much time to work in.”

The sky was overcast and cloudy that morning, in harmony with the mood of the Hardy boys. They found it difficult to be cheerful after the reverse they had just suffered.

“I’ll bet there isn’t even a railway here,” grumbled Joe.

“And our roadster is miles away.”

“What a fine fix we’re in!”

“Perhaps they’ll come back,” remarked Frank, trying to be optimistic.

“They’re gone for good.”

The Hardy boys crossed a rustic bridge over a stream and went up the dusty road into the village. It was only a small farming town and there were few people in sight. Several cars were parked in front of the small hotel.

“We might as well go in here and have breakfast,” suggested Joe. “Our sandwiches are all gone.”

They went into the hotel and entered the dining room. In spite of the disappointment they had suffered, their appetites still held good and they managed to make away with a goodly supply of ham and eggs, flapjacks and syrup, toast and coffee. The meal over, they felt better. After paying the check at the desk, they sat down to consider future plans.

The clerk told them that the village was about one hundred miles from Bayport, and that the nearest railway was four miles distant. If they hired a man from the garage to drive them to the station they could catch a train that would bring them to Bayport late that afternoon.

“I guess it’s the best we can do,” said Frank. “Mighty flat ending to our adventure.”

“Perhaps it isn’t over yet.” Joe was looking out into the street. Suddenly he clutched his brother’s arm. “Look, Frank! Do you see what I see?”

Frank looked out. He gasped with astonishment.

Across the street, lolling in the doorway of a grocery store, was a familiar figure. There was no mistaking the battered hat, the shabby clothes, the mournful and unshaven features.

“Newt Pipps!”

“He’s still here.”

At that moment the Hardy boys were perhaps the most delighted and amazed lads in the United States.

“They left him here,” said Frank. “Why, this means the others will be coming back!”

“Unless they’ve ditched Newt altogether.”

“They wouldn’t do that,” said Frank, meeting Joe’s objection. “He knows too much. He knows all about this crime they have been planning. Ducroy and Ollie Jacobs would be afraid to get rid of him now.”

“That’s right, Frank. We gave up hope too quickly. The other pair will probably be coming back to the farm to-day.”

“We’d better get back there just as quickly as we know how. We don’t want to be caught napping now.”

Newt Pipps was still standing in front of the grocery store. Apparently he had no intention of moving on. The Hardy boys knew they were risking discovery if they went out the front entrance, so they scouted around until they found a back door to the hotel and departed unobtrusively. They cut across the yard, went down a lane, and soon found themselves on the road leading back to the farm.

They were about half way back to the farm when they heard a distant droning noise. Frank looked up.

“Here comes the plane!”

A speeding shadow in the sky quickly resolved itself into the shape of an airplane, which gradually approached and began to descend in wide spirals. The boys left the road and took to the shadow of the trees, for although they knew there was little chance of being recognized from the air, they were taking no risks. The plane came lower and lower, then skimmed across the fences, coming to rest in the field near the old farmhouse.

“If this isn’t luck!” exclaimed Frank.

“They probably went away to get gas and oil. Now, if they’ll only give us a chance to get back in our hiding place again everything will be all right.”

They went on cautiously, toward the field. They had just come to the entrance of the lane leading down toward the farm when they heard voices. Frank and Joe scrambled into the hedge and hid themselves.

They were not a moment too soon.

Giles Ducroy and Ollie Jacobs clambered over the fence, only a few yards away.

“Everything is all set now,” Ducroy was saying. “We’re all fueled up, the plane is in first-class shape, and we’re all ready for the big job.”

“We’ll go back and pick up Newt now,” said Ollie Jacobs.

“He gives me a pain,” grumbled Ducroy. “If it wasn’t that he has been with us from the start I’d be tempted to drop him right now. Imagine being too frightened to go on that flight with us this morning.”

“Newt is yellow.”

“He certainly is. Well, as long as he comes with us to-night and does his part, I don’t care how yellow he is about flying.”

“Shall we come back here right away?”

“No. Some of these villagers might get suspicious. We’ll hang around town until it gets dark. Then we’ll set out. I know the exact time and place we can count on meeting this fellow and the whole thing ought to be over in twenty minutes.”

“Good,” said Jacobs.

The two men went on down the lane. They had not seen the Hardy boys hiding in the hedge. When they reached the road they turned in the direction of the village and in a few moments were lost to view.

Frank and Joe crawled out of the hedge.

“On the trail again,” said Frank.

“We shan’t have to stay hidden in the plane, after all. This is luck.”

They hastened down the lane to the farmhouse. Unwittingly, the rascals had played into their hands. They now knew that Ducroy would not start on the mysterious mission until after darkness had fallen, and they resolved to be in readiness.

“Just when we had given up hope,” said Frank, “everything gets clear again!”

“Clear enough so far,” agreed Joe. “We won’t take any chances on slipping up again. We’ll be hiding in that plane at sundown.”

The boys went back to the house and there they remained for the rest of the day. They found that from one of the upper windows of the building they could have an uninterrupted view of the road leading to the village, and they made frequent visits to this window in order to make sure that Ducroy and his companions would not steal a march on them. However, the afternoon dragged past with no sign of the trio, and it was evident that they were following their original program of loafing about the village.

The airplane, which had evidently escaped notice, rested alone in the field.

Toward the latter part of the afternoon the clouds which had been gathering all day gathered overhead and there was a light shower of rain. It passed over, but the weather became cool and blustery.

“A bad night for flying,” remarked Frank.

“If Ducroy can chance it, so can we.”

“That’s right. I hope they don’t call it off.”

“Not after waiting this long,” said Joe. “Ducroy has set his heart on this affair. It’ll take a mighty stormy night to make him quit at the last moment.”

The afternoon seemed endless, but at last Frank turned to his brother.

“We may have quite a while to wait, but I think we ought to go over to the plane now.”

“I don’t mind waiting. I’d rather wait an hour or so than be left behind, as we thought we were this morning.”

“Let’s go, then.”

The boys left the house and went over to the field. The airplane was apparently just as Ducroy and Jacobs had left it. There was no sign of anyone on the village road.

The Hardy boys climbed into their hiding place and made themselves as comfortable as possible. For the time being, they left the door open for the sake of fresh air. Minutes went by. The sky grew darker and the wind rose. Once in a while a gust of rain spattered against the wings of the machine.

At last Joe crouched forward.

“Here they come! I see a light down the road.”

He reached out and closed the door.

Breathlessly, the Hardy boys awaited the next move in their perilous adventure.