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.”