Harvey Hamilton was about to speak when Detective Pendar raised a warning hand.

“Sh!” he whispered; “some one is in the hall.”

The youth listened intently, but could not detect so much as the “shadow of a sound.” None the less, his guest was right.

“He has gone by; listen!”

The faintest possible noise, as if made by some one opening and closing a door with the extremest caution, came to their ears.

“It’s one of them,” remarked the detective, in the same almost inaudible tone; “let’s sit as near together as we can, and not raise our voices above a whisper. I allowed you to do so a few minutes ago, because there were no listeners.”

“Are those two watchers as you call them staying at the hotel?”

“They occupy the fourth room beyond.”

“And my negro lad has the third.”

“And I the second; so we are all neighbors.”

“How will you manage to leave without detection?”

“I am used to that kind of business,” replied Pendar with a smile; “give it no thought. Let us return to the matter in which you are as much interested as I. My proposal is that in sailing over the surrounding country, you scrutinize it, so far as your keen vision, assisted by your binoculars, will permit, in search of the headquarters of this gang.”

“How shall I recognize the place if I see it?”

“You will have to follow the law of probabilities. The woods are uninhabited, except in the eastern part—that is, in this direction. If you observe any old house or cabin that shows evidence of being occupied, probably it’s the place for which we are looking. Locate it definitely, and then we shall have something upon which to act. As soon as you report to me, I’ll move with all the vigor and common sense at my command.”

Here was the proposal as clearly as it could be put. Harvey nodded his head several times and compressed his lips, as does one who is in deadly earnest.

“Heaven grant that I shall be able to do something.”

“Then I was not wrong in assuming you were interested in the cause of justice?” remarked Detective Pendar.

“Not by a large majority.”

“Whoever has a hand in restoring the little girl to her parents will receive a munificent reward. Perhaps this fact may be of interest to you.”

“None whatever. Now that I shall undertake the task, we must have an understanding; suppose I discover such a place as you mention, while cruising aloft, how am I to communicate with you without drawing suspicion to myself?”

“There will be no trouble in that. You can return to the hotel, as will be quite natural for you to do, take a room under some pretense such as not feeling well, and I shall get to you without much delay. That done it will not be long before we formulate a plan of action.”

“Will my negro prove any handicap to me?”

“On the contrary, I am hoping he will be of help.”

“In what way?”

“It is impossible for him to be secretive or cunning; he is so open that his honesty speaks for itself; no one can doubt that you and he are on a little outing, with no purpose except enjoyment.”

“You have gauged his character correctly.”

“As I did yours.”

“Don’t be too certain of that; you were correct at least in believing you would enlist my efforts in your work.”

“When will you be ready to begin?”

“To-morrow morning,—provided the weather proves as clear as that old farmer declared it would be.”

“I heard his prophecy; his neighbors believe him infallible; I think you can count on favoring conditions. Bear in mind that your task is simple. You cannot halt and rest in the air, because you have to travel rapidly to sustain yourself, but you see the enormous advantages your position gives you. Wherever a house, even the smallest one, stands in the woods, the roof or some part of it must be visible from above. The abductors of the child will treat her well so long as there is a prospect of obtaining the ransom, for it is to their interest to do so. There must be cooking done in the dwelling, and the smoke will show; washing and other things are necessary,—all of which you can learn without the aid of glasses from a perch of several hundred feet. Are you acquainted with an aviator known as Professor Morgan?”

The abrupt question startled the youth.

“I met him last night and again this forenoon. He is a crank.”

“Rather; his mind is unbalanced, but for all that it is a brilliant intellect which has been knocked topsy-turvy by studying out inventions in aviation.”

“And he has made some wonderful ones. He told me he had discovered a chemical which mixed with gasoline will keep him in the air for twelve hours, and he is confident that he will soon double and triple its effectiveness. He has already learned how to sustain his machine for some time motionless.”

“Have you seen him do it?”

“I have,” and Harvey related the incident of the Professor dropping the giant crackers among the group on the edge of the wood.

“It is a most extraordinary achievement. I suppose he has managed to secure in some way the action of supports which operate like the wings of a bird, when he holds himself stationary in the sky.”

“Furthermore, he runs his machine without noise, which is another feat that no one else has been able to attain. It seems to me also that his ‘Dragon of the Skies,’ as he has named it, can travel faster than the swiftest eagle.”

It was in the mind of Harvey to ask the detective how he came to form the acquaintance of Professor Morgan and to inquire whether he knew the crank was in Chesterton at that moment, or had been there during the afternoon; but, as the caller did not volunteer the information, the youth forbore questioning him.

“We shall not forget that whenever and wherever we meet outside of this room, it will be as strangers. If you wish to speak to me on anything, you will take off your cap and scratch your head. If I see that, I shall accept it as notice that you have something important to say. As soon as you can do so without attracting notice you will go to your room. When the coast becomes clear I shall follow you, but prudence may require me to delay doing so for an hour or for several hours.”

At that moment both were startled by a loud knock on the door. On the instant, Detective Pendar whispered:

“Make believe you are asleep.”

Waiting, therefore, until the summons had been twice repeated, Harvey asked mumblingly:

“Who’s there?”

“It’s me, Bunk.”

“What do you want?”

“Didn’t yo’ tole me dat I warn’t to bodder yo’ and yo’ would call me in de morning?”

“Of course I did; what’s the matter with you?”

“I woke up a little while ago and couldn’t disremember for suah what it was yo’ tole me, so I slipped to yo’ door to find out. Dat’s all; good night!”

And his heavy tread sounded along the hall to his door through which he passed. The colored youth had slept so much during the day that he needed little more refreshment of that nature.

“What do you think of that for stupidity?” asked Harvey.

“I am not surprised. I do not recall that I have anything more to say. Will you be good enough to glance up and down the hall in search of anything suspicious?”

The detective himself noiselessly opened the door. Harvey stepped outside and stood listening and gazing toward the rear through the dimly lighted avenue, that being the direction in which the rooms referred to were situated.

“I cannot see or hear anything——”

Turning to face the man whom he addressed, and whom he supposed to be standing directly behind him, Harvey saw nobody. The room was empty. The amazed youth looked the other way, where the stairs lay. He was barely in time to catch a glimpse of his caller in gray as he turned the short corner and disappeared down the steps like a gliding shadow.

“That beats everything,” remarked the wondering young aviator, who now locked his door and prepared for bed.

It was a long time, however, after he turned off the light and stretched out on the soft mattress before he was able to woo slumber. Now that the detective had recalled the kidnapping of the Hastings child in Philadelphia, many minor particulars came back to the youth. All these helped to stir his feelings, until he longed for the morning when he could begin his work of bringing the unspeakable miscreants to justice. He comprehended vividly the anguish of those stricken hearts in their luxurious home, and shuddered to think that his own sister Mildred might have been the stolen child.

With his thoughts flitting with lightning rapidity from one subject to another, Harvey regretted that he had not questioned the officer about Professor Morgan. It would be interesting to learn how the two had become acquainted.

“I wonder,” added our young friend, following one of his innumerable whimsies, “whether the Professor is on this job too. He seems to be lingering in these parts, and he certainly has advantages which can never be mine. Perhaps when I called to him, he feared it would complicate matters if I was allowed to mix in. What’s the use of guessing?” he exclaimed impatiently, as he flung himself on his side and tried for the twentieth time to coax gentle slumber to come to him.

The coquettish goddess consented after a time, though the hour was past midnight when the youth closed his eyes. Such being the situation, it is not strange that Bohunkus Johnson was the first out of bed in the morning, and down stairs. He was thinking of the aeroplane and fearful that it had been molested during the night.

“I orter watched it agin,” was his thought as he dashed out of doors.

A few minutes later, Harvey Hamilton was startled by footsteps rushing along the hall, followed by a furious thumping on his door.

“Git up, Harv, quick!” he shouted; “somebody has busted de airyplane all to flinders!”