That watchman of yours is not the keenest-eyed fellow in the world." Some time later, just as the town clock finished booming the hour of midnight, the officer touched the arm of his companion, who said,-- "I haven't noticed anything; what is it ?" "Did you hear some one walk past ?" "Yes; the footfall sounded plainly enough: what of it ?" "That is the third time that man has gone by.

He is on the alert." "It may have been different persons." "It was the same man--sh! there he comes on the porch." In the stillness of the night the sound was plainly heard.

The next moment a key turned in the lock of the door, which was silently shoved inward.
The visitor, whoever he was, acted with the coolness of a professional.

He entered by the main door, so, if it chanced that any one saw him, he could explain the cause of his visit.

At the same time, he made as sure as was possible that no one did see him.