“I—I must confess I don’t understand,” said the colonel, looking bewilderedly from one to the other of his two companions.

“Then let me enlighten you.” And, supplemented from time to time by Jack, the doctor gave a concise account of the incidents leading up to the discovery of Jarrold breaking into the colonel’s cabin.

The officer could hardly believe his ears.

“Of course I have suspected Jarrold all along, and cannot be too grateful to this young man for his vigilance,” he said; “but the diabolical ingenuity of the man is beyond me.”

“He ought to be in irons at this minute,” asserted the doctor, “but so far as I can see, he has covered up his tracks so cleverly that we have nothing upon which to base a complaint against him.”

“At the present time, no, unfortunately,” said the colonel reluctantly. “And if it had not been for Mr. Ready, here, the whole plot might have proved a complete success.”

“I think it is reasonably certain that when you awakened, which might not have been till late to-morrow morning, you would have found your papers gone,” said the doctor.

“But in that case, I should have instantly suspected Jarrold,” was the reply. “And exercising my authority as an officer of the United States army, I could have had him detained under suspicion while his baggage and his person were searched.”

“I am afraid that that would have been very much like looking for a needle in a haystack,” said Dr. Flynn. “A rascal as clever as he is would have found some way to dispose of the papers, where it would be highly improbable that they could be found.”

“You are right,” agreed Colonel Minturn. “Well, gentlemen, I think that for the sake of all concerned, we had better keep this secret among us three and await developments.”

“But Jarrold knows that Ready suspects him,” objected the doctor.

“Oh, well, for that very reason, he won’t do any talking,” was the colonel’s response. “We must watch and wait, and the next time catch him red-handed.”

“Then you think he will make another attempt?” asked Jack.

“I have not the slightest doubt of it. Whatever nation is paying him, it has set a high price on the successful issue of his venture; and he will stop at nothing to put it through, if I have any knowledge of the man,” was the response.

“I think the best thing we can all do now is to turn in,” said Dr. Flynn.

This was generally agreed and good-nights were said; but before Jack sought his cabin, he visited the doctor’s room, where his face was attended to so as to leave hardly any marks of his encounter with Jarrold.

The latter did not appear the next day, but his niece, radiant and smiling, was at breakfast as if nothing had occurred. Jack looked at her wonderingly. He had not the slightest doubt that her part in the plot had been the cry of “Fire”; but she appeared as carefree and debonair as if she had nothing more important on her mind than making a charming appearance.

Jack could not help grinning to himself when Jarrold did not come down.

“I guess I gave him something to think about,” he remarked with a chuckle to Sam, as the two discussed the subject.

Jarrold appeared the next day. A dark mark under his left eye was the only visible sign of the encounter in Colonel Minturn’s cabin. He studiously avoided the other passengers, however, and spent most of his time pacing the deck with his niece.

The weather was steadily growing warmer now. Porpoises appeared in rolling, leaping schools, and flying fish were stirred up in whole coveys by the ship’s bow. The officers donned white uniforms, as did our wireless boys, and everything indicated that the steamer was entering the tropics.

It was Jack’s first voyage into such regions, and both he and Sam thrilled with the anticipation of seeing the new sights and people. But all the time, Jack was aware that under their feet was a smoldering volcano. Covered for a time, and blanketed, it was still smoldering, of that he was certain. He caught himself wondering uneasily what form the next attempt would take.

It was his watch one night and he was turning over these things in his mind as the ship plowed steadily onward, when, on going to the door of his cabin for a breath of fresh air, he was surprised to see, not far off, the green starboard and white mast headlights of what, from the distance between the lights on her fore and main masts, appeared to be a fair-sized steamer. She was steaming in the same direction as the Tropic Queen and going quite as fast.

Now, under ordinary circumstances, the sight of another craft on the same course would not have astonished one. But nowadays, when almost every ship is equipped with wireless, the operators of most vessels know precisely what craft are in their vicinity. Even in the case where ships are slow, and not equipped with radio apparatus, they usually signal, by day or night signals, to craft which have wireless, and ask to be reported. So that the sight of this stranger, moving along parallel with the Tropic Queen, gave Jack what was not exactly a thrill, but a sensation of vague uneasiness.

All at once, on her bridge, a red light began to flash. Like a blood-shot eye it winked through the dark night.

“By Jove, signals!” exclaimed Jack.

He got his signal code book and was able to read off, by his knowledge of Morse, the letters and words the strange craft was sending, as distinctly as if they had been printed. But they simply formed a meaningless jumble.

“It’s a code message to someone on board this ship,” muttered Jack to himself, as the crimson eye ceased to wink.

As it stopped transmitting its untranslatable—except to one who held the key—message through the darkness, the strange ship began to drop back under reduced speed. Whatever its mission, it had been accomplished. That much was plain. Jack wished that the jumble of words before him was as clear.

He sat there racking his brains over the matter till almost midnight, when Sam relieved him. The assistant operator looked at the message, over which Jack was knitting his brows, with astonishment.

“What in the world is that?” he asked.

“I wish I knew,” was Jack’s enigmatic reply, “but there’s one man on board this ship who does, and I’m inclined to think that his name is James Jarrold.”