Bill Watson was quite familiar with the plan of the city in which the circus was then playing. He had been there before with the show, and had once spent a week there, having been taken ill, and unable to go on. So this accounted for his knowledge of the eccentric Mr. Clark.

“What sort of man is he?” asked Benny, as, with Helen, he hurried on with the fun-maker.

“Well, I never heard that he was really dangerous,” answered Bill. “But he may be, for all that.”

An exclamation came from Helen—a cry of alarm.

“Oh, that doesn’t go to show that he’d harm Joe,” said Bill quickly, realizing that he had made a mistake. “Besides, Joe is quick and clever, and he’s got powerful fists. I guess he’d leave Clark at the first suspicious sign. If trouble did start Joe could take care of himself.”

“Of course!” confirmed Benny, for he saw Bill winking at him behind Helen’s back, and the human fish guessed this was what Bill wanted him to do.

“Well, I hope he’s all right,” observed the girl, with a sigh. “Let’s hurry on. Where are we going, Bill?”

“First to the old Clark mansion. It’s most likely that he’d get Joe to go with him there, if anywhere.”

“Yes, I think I heard them say something about going to Mr. Clark’s house,” averred Helen. She was nervous and excited, but tried not to show it as they hastened on.

“Is it far away?” asked Ben.

“It’s quite a way out,” Bill said. “I guess we’d better take a carriage—a closed one if we can get it.”

He had a double object in this. One was to gain time, and the other was to have a conveyance at hand in case anything had happened to Joe. They found a hack at the depot and were soon speeding on toward the outskirts of the city. The driver looked rather queerly at Bill when he gave their destination.

“’Tisn’t very often I get an order to go out there,” he said. “Folks don’t generally call on that crank.”

“Well, we have a little business with him,” Bill answered, noncommittally.

Bidding the driver of the hack to wait for them, Bill, Helen and Benny went up the weed-lined front path. A knock on the door brought no answer, and a pull at the bell handle disclosed the fact that it was not connected with anything that would produce a ring.

“I guess we’ve got to break our way in if we can’t find an open window,” Bill remarked. “It’s going contrary to law to break into a man’s house, but I guess the circumstances justify us in this case.”

“Here’s a window with some panes of glass out,” called Benny, who had gone around to the side of the house.

“Can you reach in and turn the catch?” the clown asked.

“Yes,” answered Benny. A moment later he had leaped into the house, from which came no sound. And no sooner had Benny entered than he called out:

“Hurry, Bill! There’s something queer been going on here. I can smell ether or chloroform. Come on.”

Bill scrambled in after the human fish. Helen called to them in alarm to know what had happened, but the clown told her to stay outside—that they would soon be back.

Calling Joe’s name, Bill and Benny rushed through the rooms on the lower floor. There was no answer to their hails, and no one appeared to question their right to enter.

“Up-stairs!” cried Bill. “He must be there if he isn’t down in the cellar—that is, if he’s here at all.”

“I think he is,” Benny said.

Up the stairs, partly chopped away, they hastened, using such care as was necessary, and their first sight was of a closed door with a key in the lock.

“The smell is stronger here,” Benny said. “I believe this is where he is.”

It was the work of but a moment to turn the key and open the door, and there the rescuers, somewhat overpowered by the strong and sickening odor, saw Joe lying in a heap on the floor.

“Out with him! Quick! To the fresh air!” cried Bill. He and Benny carried the unconscious lad down a rear stairway which was in better shape than the front one. They opened the front door, which was fastened with a spring lock, and lay Joe down on the front porch.

“Is he—is he——” began Helen, but she could not frame the sentence.

“He’s breathing,” said Bill. “I guess he’ll come around all right. But I can’t understand what happened.”

“Maybe we’d better get him to a doctor,” suggested Benny.

“Yes, I guess so,” agreed Bill. “No, wait—he’s opening his eyes. If we had some water it might revive him.”

“I’ll see if I can find any!” Helen cried, eager to help.

She darted into the house and made her way to the kitchen, whence she presently emerged with a pitcher of water she had drawn from the sink faucet.

Some of this sprinkled on Joe’s face, and a little given him to drink, helped wonderfully in the work of revivification the fresh air had commenced. The lad managed to rise to a sitting position, but there was a dazed look on his face.

“How did I get here?” he asked slowly. “How did you get here?”

“We don’t know much, except that we came to get you,” said Bill. “Are you hurt? Do you think you’re coming around all right, or shall we get a doctor?”

“I—I guess I’m all right,” Joe answered. “I’m not hurt, that’s sure. I was just overcome by some gas or ether.”

He drank some more of the water and then, at Bill’s suggestion, he walked around a bit to start his blood to circulating. In a little while some color came into the boy’s pale cheeks, and in a few minutes he declared he felt almost like himself again.

“But it was a queer experience,” he declared. “I can’t understand it at all. Did you see anything of that madman?”

“Clark, you mean?” asked Bill. “No, he seems to have run away. He is just what you say—a madman.”

“A dangerous lunatic,” agreed Joe. “He ought to be in an asylum. The idea of thinking I stole his flying machine invention!”

“Let’s get back to the show,” proposed Bill. “You can tell us the story on the way back in the carriage. Are you sure you don’t need a doctor?”

“Sure!” Joe answered, his strength of voice showing that he was rapidly improving.

The hack driver looked closely at his fares as he drove them back, but they did not satisfy his curiosity, for they did not want the story to be made public—at least not at present.

Joe told the story from the beginning. Helen sat near him in the carriage, and he reached out occasionally and touched her hand.

“And when I felt myself keeling over in a sort of faint,” Joe concluded, “I didn’t know what to make of it. The overpowering odor, whatever it was, seemed to come from some hidden pipe. It’s a mystery.”

“We’ll have it looked into by the proper authorities,” said Bill. “It isn’t safe to allow that lunatic at large.”

“How did you know where I was?” Joe asked.

“It was Helen,” said Benny; and when he told how the rescue had been brought about Joe indicated part of his thanks to the girl by an eloquent look and a warm pressure on her hand.

“It was just by chance that I overheard you say where you were going,” put in Helen.

“But what gets me,” said Joe, “is why he had that queer room in his house—a room like a prison vault.”

They learned the reason for that a little later, when Bill laid the facts before the police authorities. Then the whole story was told, but no public complaint was made against the lunatic, as Joe and the other circus folk had no time to stay to press the charge.

But the police said they would have the madman taken into custody and sent to an asylum as soon as they could find him, though for the present he seemed to have disappeared.

The story of the unfortunate Mr. Clark was this: He was a wealthy man, as he said, and he had invented several machines. But he lost his reason, and at that time his family, disliking to send him to an institution, had had a strong room fitted up in the old homestead. The room was lined with steel, for Mr. Clark was of such a mechanical turn of mind that he would have escaped from an ordinary apartment.

At times he became so violent that it was dangerous to go into the same room with him, so a hidden pipe was arranged in order that a quieting and harmless gas might be introduced into his vault. This would cause him to sleep, and he would then be quiet and apparently rational for weeks at a time, seeming as sane as any one.

But finally all his relatives died, and the authorities, after one of the unfortunate man’s outbreaks, sent him to an asylum. Treatment there seemed to effect a cure, and he was released, but only to go back again later. This occurred several times, but on the occasion of the man’s attack on Joe, the lunatic had managed to make his escape from the institution.

Just how Mr. Clark got the idea that Joe had stolen his invention was, of course, only to be guessed at. It was one of the queer kinks in his brain. But he seemed to want to get rid of Joe, and knowing of the hidden pipe leading to the vault had put some ether in it instead of the harmless gas that had been used on himself.

Then he had evidently run away, leaving Joe to his fate; and only for Helen’s wit, and the quick work of Bill and Benny, there might have been a different ending to the story.

During his sane, and perhaps during some of his insane, spells Mr. Clark would potter and tinker away at his “inventions” in the queer vault he made his workshop, and whither he had lured Joe. “Well,” said the chief of police, to whom complaint was made about the lunatic, “we’ll put him away as soon as we can. And the old house is soon to be torn down, so there’ll be no more danger there.”

“Then he told the truth about that,” remarked Joe.

“Oh, yes. He is cunning like all insane persons, and speaks the truth at times. It’s a sad case, but I’m glad you got out all right.”

Jim Tracy, when told of what had happened, wanted Joe not to do his turns that night. But our hero, after a cold shower bath and a good meal, said he felt as well as ever, and would not disappoint the crowds. Accordingly, he performed his motor-cycle and flying feats, but he only did part of the tank act, not staying under for any great length of time, as he did not want to tax his lungs, which showed some slight effects from the ether.

The show moved on, but later Joe and his friends learned that the unfortunate Mr. Clark had been sent to an institution, whence there was little hope of his coming out.

“I wish I knew his secret of a powerful and light storage battery,” said the young circus performer. “I’ll need it if I want to make a bigger Bat.”

“Are you going to keep on with the circus?” asked Helen.

“Yes, I think I shall. I’ve a lot of plans in my head for a bigger and better show if I can ever raise the money. I just wish my English inheritance would ‘make good.’ I’d use that money in the circus, and I’d build a bigger flying machine. Would you double up with me in that act, Helen?”

“I don’t know,” she answered hesitatingly. “Now that you are one of the owners, and when you have a bigger show, you may have no use for a performer like me.”

“The day will never come when I won’t want you, Helen,” said Joe in a low voice. “But I guess it will be a long while before I get enough money to do what I want.”

It was about a week after this that something came to Joe’s attention which caused him to do some hard thinking. He had subscribed to a London paper some time before because of his interest in English affairs. Occasionally the copies went astray in the mail on account of Joe’s travels, but this number came safely with some letters. And in reading the journal Joe saw a notice to the effect that charges of professional misconduct were to be made against a lawyer named Kent Bolling.

“Why, that’s my lawyer!” exclaimed Joe. “I wonder if he is dealing straight with me. I’ve got to look into this thing. It seems suspicious to me. I’ve got to do something!”