It was the day following Jack’s stirring adventure, which had left no more serious consequences to him than bruised hands and knees. He was sitting in the wireless room listening to the uproar outside. For the Tropic Queen was coaling, and the shouts of the negroes and the roar of the coal as it shot into the bunkers filled the air.

Sam was ashore and so was De Garros. They had gone to communicate with the authorities; but had found the Colonial police not much interested. Jack felt drowsy. It was getting late in the afternoon. Soon the swift tropic dusk would drop like a pall.

To keep awake, he decided to take a turn along the decks. He descended to the promenade deck and walked briskly up and down.

“Since we don’t sail till to-morrow, I guess I’ll go ashore this evening,” he decided to himself. “It’s too lonesome on board. Everybody’s gone ashore for that big ball at the hotel to-night.”

But he decided to wait for the return of Sam and De Garros before leaving. It grew dark, and they had not come back. Jack was about to scribble a note and leave it in the wireless room, explaining that he had tired of waiting and gone ashore, when a roughly dressed man brushed by.

It was too dark to see the fellow’s face, but he appeared to be a sailor. Jack thought little more of the incident and went to his room to change his uniform for street garments. He was descending the stairs again to the main deck, bound for the gang-plank, when he was startled by a sudden sound.

It was the dull booming noise of an explosion, and it appeared to come from some place on board the ship.

For a minute or two he stood still, trying to locate the sound. As he stood at pause, a figure darted from the purser’s room. It was that of the roughly dressed sailor who had shoved past the boy a short time before. From the purser’s room there rolled a dense cloud of smoke. It reeked of dynamite.

Jack flashed along the deck. There was a light inside the office of the ship’s bookkeeper and cashier—which is what a purser amounts to, besides being a banker and money changer.

The boy saw in an instant what had happened.

The safe had been dynamited. Its door hung by one hinge. The air was full of smoke and the acrid reek of the explosive.

Jack knew that large sums of money and jewelry were frequently in the safe, and no doubt the bold thief had made off with an armful of loot. He wasted no more time investigating, but at top speed dashed for the gangway.

On the deck two big arc-lights shimmered whitely. Under their glare he saw a darting figure making for the shore end of the dock. He noticed that the man was heavily bearded and wore the rough clothes of a sea-faring man.

“Stop thief! Stop!” shouted the boy; but the man kept right on with his head down, clutching something that he had concealed in his loose sailor’s blouse.

There was an old watchman at the gates of the dock. He put out a feeble arm to stop the marauder, but a terrific blow in the face knocked him off his feet.

The man darted on. Jack was close on his heels. They passed through the gate with only a few feet separating them.

A hack, apparently stationed there in preparation for the flight, was waiting. The black-bearded man leaped into it. But, by providential luck, another night-prowling rig came along at just that moment, its driver nodding sleepily.

As the first rig dashed off, rattling loudly over the rough street, Jack leaped to the front seat of the second, beside the astonished driver.

He seized the reins from the man and brought down the whip on the horse’s back with a crack that made the animal jump. It leaped forward with a jerk that seemed as if it would disrupt the crazy harness.

The man began to yell with dismay. But Jack quickly checked him.

“It’s all right. You’ll be well paid for this. That man in the hack ahead of us is a thief.”

“Gelagoodness, Busha, I t’ink you was de thief, when you come leaping board mah cab de way you do.”

The man was reassured by Jack’s frankness, however, and they flew down the street at top speed after the other cab. The way lay along the deserted water-front, by coal docks, warehouses and gaunt traveling cranes. There were few lights and the road was rough and uneven. The old hack jumped and bounced about like a ship at sea.

Suddenly something happened to the cab in front. One of its wheels caught in a rut as it was passing a dock. The wrench proved too much for the rickety old contraption, and the wheel went spinning off its snapped axle, while the black-bearded occupant was flung into the road like a stone from a catapult.

He lay still a moment while the driver of the wrecked vehicle in vain tried to stop his horse. Sagging to one side on its broken axle, the hack vanished in the distance with its runaway steed’s legs working like piston rods.

Jack was out of the following rig in a flash. He rushed up to the black-bearded man’s side just as the other rose to his feet.

It was not till that moment that Jack recollected that he had no weapon with him.