"Look here," cried Roy, indignantly wiggling in the officer's strong grasp, "can't you see that this is all a mistake? If you hadn't grabbed me, I could have caught that impostor."

A great light seemed to break on Lieut. Bradbury.

"Why, bless my soul," he exclaimed, "that's so. I can see it all, now. That chap who got away wore a gray suit, while yours is a blue serge, isn't it?"

"It was, before I was thrown into that cellar," said Roy ruefully.

The moon was shining brightly now, and he saw that, in the semi-darkness, it would have been easy to mistake his blue serge, dust-covered as it was, for one of gray material.

"Tell me exactly what has happened," urged the officer. "I must confess I am in a mental whirl over to-night's happenings."

Roy rapidly sketched the events leading up to his capture and imprisonment, not forgetting to lay the blame on himself for being so gullible as to be led into such a pitfall.

"Not a word more of self-blame, my boy," cried the young officer warmly. "Older persons than you would have stumbled into such an artfully prepared snare, baited as it was with the hope of catching Mortlake in a plot to destroy your aeroplane. But now I'm going to tell you my experiences, and we can see if they dovetail at any point."

But when Lieut. Bradbury concluded his narrative, they were still at sea as to the main instigator of the plot. Of course, the finger of suspicion pointed pretty plainly to Mortlake, but the rascal had covered his tracks so cleverly that neither Roy nor the young officer felt prepared to actually accuse him.

"But I can't see how an ordinary workman would have had either the brains or the motive to direct such an ingenious scheme to discredit me in your eyes," concluded Roy, as they finished discussing this phase of the question.

"Nor I. But hark! Somebody's shouting. It must be Mortlake. Yes, it is. Hull—o—a!"

"Hullo—a!" came back out of the night.

"Come, we will retrace our steps to the auto and meet him there," said the lieutenant.

"I wonder if he'll have the face to brazen it out?" thought Roy, by which it will be seen that his mind was pretty well made up as to the "power behind" the night's work.

"Couldn't come near the fellow," puffed Mortlake, as they came up. "He ran like a deer. But—great Christmas—you've had better luck, I see!"

For an instant, even in the semi-darkness, Roy saw the other's face grow white as ashes.

"He thinks that Lieut. Bradbury has caught my impersonator," was the thought that flashed through the boy's mind.

But the same sudden radiance that had betrayed Mortlake's agitation also showed him that it was the real Roy Prescott he was facing. Instantly he assumed a mask of the greatest apparent astonishment.

"Roy Prescott, I am really amazed that you should be implicated in such a——"

"Save your breath, Mr. Mortlake," snapped out the lieutenant, and his words came sharp as the crack of a whip; "this is the real Roy Prescott, and he has been the victim of as foul a plot to blacken an honest lad's name as ever came to my knowledge. The young ruffian who impersonated him to-night has escaped."

"Escaped!" exclaimed Mortlake, but to Roy's quick ears, despite the other's attempt to disguise his relief, it stood out boldly.

"Yes, escaped. Partly owing, I confess, to my overzealousness. There has been foul play here somewhere, Mr. Mortlake."

The officer's voice was stern. His eye flashed ominously. Just then old Mr. Harding came puffing up.

"Oh, so you got the boy, hey?" he cackled, but Mortlake shut him off with a quick word.

"No. This is the real Roy Prescott. It seems that a trick has been put up on us all. The lad we mistook for Roy Prescott was some one impersonating him. This lad has been the victim of a vile plot. While we were watching here for his supposed appearance and the revelation of his treachery, some rascals had locked him in a cellar."

The lieutenant's words were hot and angry. He felt that he was facing two clever rascals, whose cunning was too much for his straightforward methods.

"You—you amaze me!" exclaimed old Mr. Harding, looking in the moonlight like some hideous old ghoul. "What game of cross-purposes and crooked answers is this?"

"That remains to be seen. I shall see to it that an investigation is made and the guilty parties punished."

Was it fancy, or did Roy, for a second, see Mortlake quail and whiten?

But if the boy had seen such a thing, the next instant Mortlake was master of himself.

"It seems to me to have been a plot put up by my workmen," he said. "If I find it to be so, I shall discharge every one of them. Poor fellows, in their mistaken loyalty to me, perhaps they thought that they were doing me a good turn by trying to discredit my young friend—I am proud to call him so—my young friend, Prescott."

For the first time, Roy was moved to speak.

"I hardly think that your workmen were responsible, Mr. Mortlake," he said slowly and distinctly.

"You do not? Who, then?"

"I don't know, yet, but I shall, you can depend upon that."

"Really? How very clever we are. Smart as a steel trap, hey?" grated out old Harding, rubbing his hands. "Smart as a steel trap, with teeth that bite and hold, hey, hey, hey?"

"Instead of wasting time here, I propose that we at once go to the house in which Roy was confined, and see if we can catch the rascals implicated in this," said Lieut. Bradbury. "Can you guide us, my boy?"

"I think so, sir. It's not more than half an hour's tramp from here," said Roy. "Let's be off at once, otherwise they may escape us."

"Ridiculous, in my opinion," said Mortlake decisively. "Depend upon it, those ruffians have found out by now how cleverly the boy escaped them, and have decamped. We had much better get back to town and notify the police."

"I beg your pardon, but I differ from your opinion," said the naval officer, looking at the other sharply. "Of course, if you don't want to go——"

"Oh, it isn't that," Mortlake hastened to say. "I'm willing, but Mr. Harding. He is old, and the night air——"

"Mr. Harding can remain with the automobile. There are plenty of wraps in it. Come, Roy. Are you coming, Mr. Mortlake?"

"Yes, oh, yes. Mr. Harding, you will make yourself comfortable till we return."

Having said this, Mortlake came lumbering after the other two, as eagerly as if his whole soul was bent on capturing the two men who had been carrying out his orders.

"I've got a revolver ready for them," he volunteered, as the party plunged through the woods along the little track Roy had followed.

"Take care it doesn't go off prematurely and alarm them," said the officer. "We don't want to let them slip through our fingers."

"Of course not; I'll be very careful," promised Mortlake.

They trudged on in silence. Suddenly Roy halted.

"We're near to the place now," he said.

"Advance cautiously in single file," ordered the lieutenant. "I'll go first."

In Indian file, they crept up on the house. Its outlines could now be seen, and in one window a ruddy glow from the lamp the two abductors of Roy had kindled. Evidently they had not yet discovered his escape.

All at once Mortlake, who was last, stumbled on a root and fell forward; as he did so, his revolver was discharged twice. The shots rang out loudly in the still night.

Instantly the light was extinguished. The next instant two dark figures could be seen racing from the house. Before Lieut. Bradbury could call on them to halt, they vanished in the darkness and a patch of woods to the north.

"What a misfortune!" exclaimed Mortlake contritely, picking himself up.

Lieutenant Bradbury could hardly restrain his anger.

"How on earth did you happen to do that, Mortlake?" he snapped. "Those two shots alarmed those rascals, and now they're gone for good. It's most annoying."

"I appreciate your chagrin, my dear Bradbury," rejoined Mortlake suavely, "but accidents will happen, you know."

"Yes, and sometimes they happen most opportunely," was the sharp reply.

Mortlake said nothing. In silence they approached the house, but nothing save the pack of greasy cards, was found there to indicate the identity of its late occupants.

There was nothing to do but to return to the automobile. They found old Mr. Harding awaiting them eagerly. He showed no emotion on learning that Roy's captors had escaped just as their capture seemed certain.

On the drive back to Sandy Beach, the old banker and Mortlake occupied the front seat, while Roy and Lieut. Bradbury sat in the tonneau. As they skimmed along, Roy drew something from his pocket and showed it to the officer. It was an object that glistened in the wavering moonlight.

"It's a woman's hair comb!" cried the officer in amazement, as he regarded it.

"Hush, not so loud," warned Roy. "I picked it up where I had the struggle with the other Roy Prescott. It may prove a valuable clue."