The marks of the carriage wheels were still fresh and they ran straight into the city.

On the pavements they were, of course, lost.

Leo was in a quandary.

He told Greson of what he had discovered, and then both of them began a systematic search for Mart.

Greson started from where the carriage had entered the city.

The young gymnast went to the exhibition grounds and attempted to trace up the man who had fired the shots at the balloon.

From one and another the young gymnast was able to trace up Porler to a third-rate boarding-house on one of the side streets.

He was about to enter the place when he saw a fellow named Danny Murphy, who was Porler's a.s.sistant, leaving in a great hurry.

"Perhaps he is going to join Porler at some place where Mart is being kept," said Leo to himself. "I'll follow him."

And follow Murphy he did.

All unconscious of being watched, Porler's tool walked half a dozen blocks until he came to the residence in which Mart was kept a close prisoner. He walked around to the rear through an alleyway.

Close behind him, Leo heard him give a peculiar knock on the door.

A moment pa.s.sed and Murphy was admitted. The back door was locked and bolted after him.

When the door had been opened Leo had caught a momentary glimpse of Porler's face.

"That settles it," he thought. "Mart is kept a prisoner right here."

Leo had armed himself, and now he walked to one of the kitchen windows.

He opened the blinds. The window itself was locked, but bringing out his pocketknife he shoved back the catch.

Another moment and the lower sash was raised and the young gymnast leaped into the house.

He did not care if his enemies were present. He was prepared to fight, if need be.

But, as he surmised, the lower floor of the residence was deserted.

With cautious steps Leo left the kitchen and walked toward the stairs leading to the next floor.

As he did so he heard the murmur of voices from above.

He went up and listened with strained ears.

"Mr. Porler, starve me or not, I will never do as you wish."

It was Mart who was speaking.

"And I say you will do so," growled Porler.

"That's right," put in Murphy. "Make the boy toe the mark."

"I will not only starve you," went on Porler, "but I will give you a taste of your old friend, the strap."

"You will not dare to touch me!" exclaimed the lad.

"Wait and see."

"My friend, Mr. Dunbar, will have the law on you for it."

"Dunbar will never help you again."

"I think he will."

The voice came from the doorway, and the three in the room found themselves confronted by Leo.

CHAPTER x.x.xIV.-THE END OF PORLER.

Porler and Murphy were taken completely by surprise when confronted by Leo.

On seeing the young gymnast, Mart gave a cry of joy.

"Oh, thank Heaven you have come!"

"Get into the corner, boy!" howled Porler.

"Don't you speak to him again," said Leo sharply. "He is no longer your prisoner."

"Ain't he? We'll soon see about that."

As Porler spoke he advanced upon Leo.

But when the young gymnast brought his weapon up within range of the rascal's head the latter quickly recoiled.

"You see, Porler, I am armed."

Murphy, who was completely dumfounded to see Leo, now came forward.

"We are two to one, young feller," he said warningly. "Yer better go slow."

"I know my own business," was Leo's quiet reply. "Mart!"

"Well?"