Once, while I stood on the watch, a sharp agony of suspense tried me fiercely.

Just as I had calculated that the time was come which would force them to depart, in order to return to North Villa by the appointed hour, I heard the slow, heavy, regular tramp of a footstep advancing along the street.  It was the policeman of the district going his round.  As he approached the entrance to the mews he paused, yawned, stretched his arms, and began to whistle a tune.  If Mannion should come out while he was there!  My blood seemed to stagnate on its course, while I thought that this might well happen.  Suddenly, the man ceased whistling, looked steadily up and down the street, and tried the door of a house near him—­advanced a few steps—­then paused again, and tried another door—­then muttered to himself, in drowsy tones—­“I’ve seen all safe here already:  it’s the other street I forgot just now.”  He turned, and retraced his way.  I fixed my aching eyes vigilantly on the hotel, while I heard the sound of his footsteps grow fainter and fainter in the distance.  It ceased altogether; and still there was no change—­still the man whose life I was waiting for, never appeared.

Ten minutes after this, so far as I can guess, the door opened; and I heard Mannion’s voice, and the voice of the lad who had let me in.  “Look about you before you go out,” said the waiter, speaking in the passage; “the street’s not safe for you.”  Disbelieving, or affecting to disbelieve, what he heard, Mannion interrupted the waiter angrily; and endeavoured to reassure his companion in guilt, by asserting that the warning was nothing but an attempt to extort money by way of reward.  The man retorted sulkily, that he cared nothing for the gentleman’s money, or the gentleman either.  Immediately afterwards an inner door in the house banged violently; and I knew that Mannion had been left to his fate.

There was a momentary silence; and then I heard him tell his accomplice that he would go alone to look for the cab, and that she had better close the door and wait quietly in the passage till he came back.  This was done.  He walked out into the street.  It was after twelve o’clock.  No sound of a strange footfall was audible—­no soul was at hand to witness, and prevent, the coming struggle.  His life was mine.  His death followed him as fast as my feet followed, while I was now walking on his track.

He looked up and down, from the entrance to the street, for the cab.  Then, seeing that it was gone, he hastily turned back.  At that instant I met him face to face.  Before a word could be spoken, even before a look could be exchanged, my hands were on his throat.