"You don't think he is likely to come in the back way?" he asked in a guarded undertone.
"There is not the slightest danger of his doing so. That would look suspicious. He will use the front door, so, if seen and challenged, he will be ready with the excuse that he has called on legitimate business of his own. At the same time, he will try to manage it so as not to be observed by any one. 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.