At midnight, while the Tropic Queen was plying ever southward through smooth seas and under a dark canopy of sky lit by countless stars, Jack left his key and, calling Sam, whose turn it was on watch, went below for his customary midnight “snack.” A sleepy-eyed steward served him in the big saloon, which looked empty and desolate with only one light in all its vastness.

Jack ate heartily and then prepared to go on deck again. He had reached the foot of the saloon stairs when a sudden sound made him pause.

It was the rustle of skirts. Jack drew back into the shadow which hung thickly over that part of the saloon. To his astonishment, for he thought that all the passengers—except a belated party in the smoking-room—were in bed, he saw that the figure which passed swiftly through the corridor beyond the staircase was that of Miss Jarrold.

She wore a white dress which showed ghost-like through the gloom, although the corridor was dimly lighted. But there was no mistaking her slender, graceful outlines and quick, panther-like walk.

Suddenly the conversation that Sam had repeated to him flashed across Jack’s mind. It had appeared to foreshadow some desperate attempt to gain whatever the pair had set their minds on. Almost beyond a doubt, these were the papers and plans relating to the Panama Canal. Jack knew that Colonel Minturn’s cabin was in the direction the girl was following.

Could it be possible that——

Suddenly a piercing shriek came, followed by cry after cry.

Jack’s heart stood still. His scalp tightened.

The cry was the most blood-chilling that can be heard at sea.

“Fire! Fire! Fire!”

Jack dashed down the passage. From every stateroom now, shouts of men and screams of women were coming. Warned by he knew not what instinct, he made for Colonel Minturn’s cabin.

It lay just around a corner of the passage. He had just gained it, when he saw a bulky figure, that of Jarrold, hurl itself against the door and go smashing through it. Jack rushed up.

Jarrold turned on him with a savage growl.

“Get away from here, boy. I’ll save Colonel Minturn. You go and warn the other passengers.”

But Jack made no move to go. Instead, he stepped into the cabin. In his bunk lay the colonel, apparently sleeping deeply. Jack shook him, but he did not move, only lay there, breathing heavily.

“This man has been drugged,” he exclaimed half aloud.

At the same instant he felt the hulking form of Jarrold fling itself at him.

“You infernal, interfering young spy,” he snarled. “Get out of here. Get back to your post. Send out an alarm of fire.”

He seized Jack with his big hands. The boy’s blood boiled. Big as Jarrold was, and powerful, too, Jack was, he thought, a match for him.

Jarrold aimed a fierce blow at him. Jack dodged it and parried it with one of his own. Then the two clinched. Jarrold’s powerful arms encompassed the boy, squeezing the breath out of him.

Outside the cabin, people in all stages of dress and undress were rushing about screaming and shouting. The whole ship was in pandemonium. Within the cabin, for Jarrold had closed the door when he followed Jack in, the two combatants, the boy and the man, fought in desperate silence for the mastery, while the man in the bunk lay with closed eyes, breathing heavily.

Back and forth they swayed till Jack suddenly wrenched himself loose. He delivered a powerful blow and stopped a bull-like rush from Jarrold. The fire, everything, was forgotten before his desire to overcome the man who had attacked him.

Jarrold was, as has been said, a bull of a man. Thick-necked, powerful and possessed of no little science, he could have torn Jack to pieces if he could have gripped him right. But Jack, once free of his clutches, was careful to avoid this.

Jack possessed no little of the science of the gymnasium, too. He fought coolly, taking every advantage of his skill. Again and again he dodged Jarrold’s mad rushes, and again and again he landed blows which seemed heavy enough to fell an ox.

But they did not appear to have any effect on Jarrold’s big frame. A mere grunt was the only sign that he had noticed them. Jack began to despair of handling his man after all.

In the struggle, furniture was smashed, Jarrold’s coat torn, and both combatants’ faces were cut and bruised. Gasping for breath, dizzy from the thundering shock of the few blows Jarrold had driven home like flesh and blood sledge hammers, Jack was about to give up, when suddenly he noticed that no one was facing him. Jarrold, breathing heavily, his face purple, lay stretched across a lounge as he had fallen.

A terrible thought flashed through Jack’s mind. Suppose he had killed him?