When the tall leader spoke in that stern voice, evidently his men knew better than to put up any further complaint. They both passed out, and Jack could hear Antoine making his way down the broad trail to gain a point where, hidden himself, he could still watch the trio of modern motor boats, and discover the first indication of any desire on the part of the crews to come ashore.

It was surely growing very interesting. Jack felt that he was being treated to a real life drama of the most thrilling description. When the boys decided to come to the St. Lawrence river for their summer outing, not one among them dreamed that before they left that region of many islands they would have run up against a series of strange adventures well worthy of being given a place in the log of the motor boat club.

Indeed, all the trouble they had anticipated was possibly frequent ructions with Tricky Clarence and his side partner, Bully Joe Brinker.

At thought of the two a sudden idea seemed to flash through the mind of Jack. He remembered the event of the dark boat, when Herb and Dick were given such a fright. At the time he had wondered whether Clarence, on his own account, could have ventured to dash by at full speed, and come within an ace of smashing into the Comfort. The new idea was along the line that perhaps the two boys might have fallen into the hands of the smugglers, who were using the Flash to suit their evil purposes!

It was so stunning a thought that Jack felt his very breath taken away. Yet after all was there anything utterly improbable about it? These men must be daring after their fashion. They were being hunted all the time by shrewd government agents; and consequently must adopt new methods of carrying on their business.

And if it were indeed true, would it not account for many things—the white face of Clarence at the time he passed the boys who were fishing—his refusal to even answer the wave of the hand they gave him—he may have been in no position at the time to appear jovial, or even half-way friendly.

Voices again!

Jack moved up to his crack, prepared to see all there was going on. Such a glorious opportunity did not come across the path of most fellows, off on their summer vacation; and he ought to improve the golden chance to the limit.

It would be folly not to admit that the boy was trembling as he crouched there, for he never denied the fact himself. But after all it was more the excitement of the adventure than any bodily fear on his part that caused this.

He had hardly settled himself comfortably when through the doorway came a stooping figure. It was a man bearing a package on his back. This he deposited on the earthen floor, and turned to assist a second fellow whose bundle seemed of even larger dimensions than the first.

One of them had also fetched a shovel along, which had a long handle. This the leader seized upon eagerly, and commenced digging in a certain corner, first removing the accumulated straw, which was apparently used as a means for hiding signs of recent disturbance.

Jack’s eyes grew hot with straining at the little crack; but he could not draw himself away; it was all so thrilling, so picturesque, that he must continue to look, no matter what the discomfort.

Now, the man with the shovel had succeeded in arriving at what seemed to be the lid of a large box. He lifted this, and one of the men tossed his bundle into a yawning aperture.

Here the stuff would lie unsuspected, until some time when the opportunity seemed ripe to dispose of it, when the deal would be completed.

Jack wondered what could be in those packages; undoubtedly something of particular value, since these men would never venture to take such chances of capture for a trifling gain.

He also found himself guessing whether the strange “professor,” whom he now knew to be a government agent, could be watching all these operations from some other friendly crack across the way.

What would he do? Having witnessed all he wished, would the other attempt to arrest these fellows? Since there seemed to be something like half a dozen of the smugglers it hardly seemed likely he would go to such extremes. Possibly he might be satisfied to capture the spoils, after the men had departed; and trust to future good fortune to arrest the delinquents later on.

One of the men left the cabin, probably to return to the upper end of the island, where the boat lay from which these packages of goods had been carried. He was in an ugly humor, judging from his manner. The stubborn way in which the motor boat boys stuck to that cove was giving these worthies a tremendous lot of unnecessary work; and it was no wonder they felt badly disposed toward Jack and his chums.

Five minutes later the second man was sent off, leaving the leader there to finish up the job of smoothing off the earth and replacing the broken straw as before.

When he had finally completed his task it would require a practiced eye to notice anything queer about the floor of the cabin.

Then he, too, prepared to depart. Jack saw him stoop down and take hold of the lantern, which had all this while been resting on the ground. In his other hand he carried the long-handled shovel with which the digging had been done.

The tall man straightened up suddenly, and his manner was that of one who had been startled. Jack knew why he should act in this way, for the same sound that had come to the man’s ears had also reached his.

It was a shrill whistle, twice repeated, and it came from the same direction in which the two men had gone a short time before.

Undoubtedly it was a signal denoting urgent need of haste. The actions of the tall smuggler would indicate as much; for he dashed out of the cabin like a shot, and Jack heard the thud as he threw the shovel into the shrubbery surrounding the lone hut.

Then followed the crashing of bushes as the man started by a circuitous route toward the upper end of the island. He must know every foot of the ground, and by taking to the open beach, could gain a given point much sooner than one who kept to the thick undergrowth.

Jack saw the lantern had been hastily dropped, though it was still burning. He was trembling with excitement, and feeling very much as though he wanted to yell at the top of his voice as he picked up this abandoned tool of the discovered smugglers.

He could hear the boys talking down there where the trio of motor boats were anchored; and could imagine how they must be wondering what all the racket on the island meant; while Josh would doubtless start in to tell them how he, Jack, had persisted in going ashore.

Some one was coming, for Jack could hear quick footsteps near by. He still held his Marlin gun, but was loath to even threaten to use it. Nor was there any need, for a moment later the moving dim figure took form, and proved to be no other than Professor Marshland.

At sight of Jack standing there, lantern in one hand and gun in the other, the gentleman allowed something like a grim smile to creep over his face, even as he came hurrying up, almost out of breath from his exertions.

“Do you know what it all means, Jack?” demanded the other, as soon as he reached the side of the boy.

Jack nodded his head eagerly.

“I was looking in through a crack, and saw what that man did. But I’m sorry he got away from you, sir,” he replied.

“I managed to capture the two fellows who left the hut!” the government agent exclaimed. “My Indian has meanwhile overcome the chap who was sent to watch your boats. But unless I can overtake the ring leader of the bunch, I shall feel that my work has not been wholly a success.”

“He headed for the upper end of the island,” Jack put in.

“Yes, and I have reason to suspect that the other two men are there with the boat. You will be surprised when I tell you that they actually turned pirates and captured the speed launch which you told me belonged to an acquaintance of yours.”

“The Flash,” echoed Jack. “No, I am not surprised, for I had begun to suspect something like that. They must have made Clarence threaten to run us down, hoping we would pull up anchor, and get away. But if that is so, you could never hope to overtake them in that slow little boat of yours.”

“Well, I should say not!” declared the other.

“Now, if it were the Wireless, for instance, you might have some chance,” Jack went on.

“Which is just the point I wanted to put up to you boys,” cried the government agent, eagerly. “Would you be willing to assist me run that clever scoundrel down? Do you think George would care to try conclusions with the Flash?”

At that Jack laughed.

“Why, sir,” he declared, “he’s been just wild for the chance, ever since we first set eyes on that narrow boat. He believes he can beat her out in a race. Suppose you come down with me right now, and we’ll ask him.”

“Thank you, Jack; it was a lucky day for me when I ran across you boys. But let us lose no time; for doubtless they’ll be off as soon as they can, knowing that the game is now up, and all that remains to them is escape.”

Nothing loth, Jack accompanied him as he started along the broad trail leading down to the cove. He could readily understand now that the revenue man must have investigated to some purpose that day while at the cabin; and knowing there were no smuggled goods in the cache then, had laid his plans to come back in the night, in the expectation of catching the rascals in the act; which was just what he had done.