As soon as Helen was out of the chair and beneath the stage an attendant closed the newspaper and wooden floor traps.  Joe then suddenly raised the veil, taking in its folds the false cap and the cross piece which had represented Helen’s shoulders.  They were thin and light—­these pieces of trick apparatus—­and no one suspected they were in the veil.  The hinged seat of the chair snapped back in place by means of a spring, and when Joe stepped aside, holding the veil, there was the empty chair; and the newspaper, which he picked up, seemed to preclude the possibility of there having been a trap in the stage.  But Joe was careful how he exhibited this paper to his audience.

And so it was that the lady “vanished.”

“And now, Joe, tell me all about it!” demanded Helen, when the circus was over for the afternoon, and the box and vanishing tricks had been successfully performed.  “What happened to your trapeze?”

“Some one spilled acid on one of the wire ropes, and it ate into the metal, corroding it and separating a number of the strands so that a little extra weight broke them,” said Joe.

“Acid on the cable?” cried Helen.  “How did you find out?”

“I just examined the wire.  I knew it couldn’t have rusted naturally in such a short time.  There was a peculiar smell about the wire, and I know enough of chemistry to make a simple acid test!  What kind of acid was used I don’t know, but it was strong enough to eat the steel.”

“Who could have put it on?”

“That I’ve got to find out!”

“Was it Harry Loper?”

“I taxed him with it, but he swears he knew nothing of it,” said Joe.  “I’m inclined to believe him, too.  I charged him with drinking, and he could not deny that.  But he said he met some old friends and they induced him to have a little convivial time with them.  No, I don’t believe he’d do it.  He’s weak and foolish, but he had no reason to try to injure me.”

“Who would, Joe?  Of course there’s Bill Carfax, but he hasn’t been seen near the circus of late.”

“No, I don’t believe it could have been Bill.  I’ll have to be on my guard.”

“Do, Joe!” urged Helen.  “Oh, I can’t bear to think of it!”

“Don’t then!” laughed Joe, trying to make light of it.  “Let’s go down town and I’ll buy you some ice cream.”

“But you’re not going to give up trying to find out who put acid on the trapeze, are you?”

“No, indeed!” declared the young performer.  “I have two problems on my hands now—­that and trying to learn how too many persons came to the circus this afternoon,” and he told Helen about the extra tickets.

“That’s queer!” she exclaimed.  “Some jinx bug must be after us!”

“Don’t get superstitious!” warned Joe.  “Now we’ll forget our troubles.  They may not amount to anything after all.”

But, though he spoke lightly, Joe was worried, and he was not going to let Helen know that.  They went into an ice-cream parlor and “relaxed,” as Helen called it.