“It is not a thief,” he said to himself, “and it isn’t any one who has designs on one of the boats.  He left that tent, but who is he and what does he want?”

The silent figure, moving rapidly forward, presently left the line of tents, and made for the cottage occupied by the doctor.

“I wonder if it is the doctor walking in his sleep?” thought Billy.  “That would be a great joke, wouldn’t it?”

He thought he saw a flash of light for a moment, but was not sure of this, and hurried on after the midnight prowler, having just time to see him enter the window of the doctor’s cottage.

“Can it be the doctor after all?” he muttered.

“That would be funny after all.  I wish I had brought my light with me.  That’s just like me, though, thinking of things when it is too late.”  He stepped under the front window of the cottage, through which he had seen the figure disappear and listened: 

“I don’t hear anything,” he muttered.  “I wonder if it could have been the doctor?  Burglars would have no good excuse for coming to the camp.  Who is it anyhow?”

Listening intently, he fancied he could hear some one moving about in the cottage, and then the steps approached the window.

He was about to step back, but was a little too late in that, as he had been in thinking of his pocket light.

In another moment some one dropped out of the window, and he was upset most unceremoniously.

The person, whoever it was, had landed on his head and shoulders, and he was thrown down in an instant.

“Hello! who is that?” he exclaimed, as he felt himself lying on the bare and rather damp ground.

Some one was struggling to his feet with a startled exclamation, and Billy snatched quickly at him, and caught a leg or an arm, he could not be certain which.

“I’ve got you now!” he cried, “and you’ve got to give an account of yourself, my man!”

The stranger, whoever he was, certainly did give an account of himself, but not in the manner which Billy meant.

There was a sudden shooting out of a brawny fist, and Billy was taken between the eyes, and for a moment saw stars.

“Ouch!” he ejaculated, letting go of the person he had seized,

Then somebody rolled him over with a quick move of the foot, and by the time the unfortunate joker arose his nocturnal combatant was out of sight, as well as hearing.

“H’m! that’s too bad!” sputtered Billy.  “I don’t know now whether it was a burglar, a nightmare, or what it was.  I think I’d better go back to bed.  Being out in the air may have done me a lot of good, but I guess I’ve had enough of it.”

With this conclusion he set out upon his return, but when he reached the line of tents was not certain whether he was in the right one or not, and began studying the appearance of things as much as he could by the very uncertain light.