But then, was it perhaps possible that this fellow, working away so unconcernedly, within arm’s-length of him, was in reality one of them, seeking to obtain admittance in this way for some reason of his own, some private treachery, it might be, or some dispute?  To Dunn that did not seem likely.  More probably the fellow was merely an ordinary burglar—­some local practitioner of the housebreaking art, perhaps—­whose ill-fortune it was to have hit upon this house to rob without his having the least idea of the nature of the place he was trying to enter.

“He might prove a useful recruit for them, though,” Dunn thought, and a sudden idea flashed into his mind, vivid and startling.

For one moment he thought intently, weighing in his mind this idea that had come to him so suddenly.  He was not blind to the risks it involved, but his eager temperament always inclined him to the most direct and often to the most dangerous course.  His mind was made up, his plan of action decided.

The scratching of the burglar’s tool upon the glass ceased.  Already he had smeared treacle over the square of glass he intended to remove and had covered it with paper so as to be able to take it out easily and in one piece without the risk of falling fragments betraying him.

Through the gap thus made he thrust his arm and made sure there were no alarms fitted and no obstacles in the way of his easy entrance.

Cautiously he unfastened the window and cautiously and silently lifted the sash, and when he had done so he paused and listened for a space to make sure no one was stirring and that no alarm had been caused within the house.

Still very cautiously and with the utmost precaution to avoid making even the least noise, he put one knee upon the window-sill, preparatory to climbing in, and as he did so Dunn touched him lightly on the shoulder.

“Well, my man, what are you up to?” he said softly.  And without a word, without giving the least warning, the burglar, a man evidently of determination and resource, swung round and aimed at Dunn’s head a tremendous blow with the heavy iron jemmy he held in his right hand.

But Dunn was not unprepared for an attack and those bright, keen eyes of his seemed able to see as well in the dark as in the light.  He threw up his left hand and caught the other’s wrist before that deadly blow he aimed could descend and at the same instant he dashed his own clenched fist full into the burglar’s face.

As it happened, more by good luck than intended aim, the blow took him on the point of the chin.  He dropped instantly, collapsing in on himself as falls a pole-axed bullock, and lay, unconscious, in a crumpled heap on the ground.

For a little Dunn waited, crouching above him and listening for the least sound to show that their brief scuffle had been heard.

But it had all passed nearly as silently as quickly.  Within the house everything remained silent, there was no sound audible, no gleam of light to show that any of the inmates had been disturbed.