It was characteristic of Tavernake that he was prepared to obey without a second’s hesitation.  The opportunity, however, was denied him.  The events which followed came and passed like a thought.  A blow on his left wrist and the whistle fell into the road.  A dark figure had sprung up, apparently from space; a long arm was twined around Pritchard’s neck, bending him backwards; there was a gleam of steel within a few inches of his throat.  And then Tavernake saw a wonderful thing.  With a turn of his wrist, Pritchard suddenly seemed to lift the form of his assailant into the air.  Tavernake caught a swift impression of a man’s white face, the head pointing to the street, the legs twitching convulsively.  Head over heels Pritchard seemed to throw him, while the knife clattered harmlessly into the roadway.  The man lay crumpled up and moaning before the door of one of the houses.  Pritchard sprang after him.  The door had been cautiously opened and the man crawled through; Pritchard followed; then the door closed and Tavernake beat upon it in vain.

For several seconds—­it seemed to Tavernake much longer—­he stood gazing at the door, breathing heavily, absolutely unable to collect his thoughts.  The whole affair had happened with such amazing celerity!  He could not bring himself to realize it, to believe that it was Pritchard who had been with him only a few seconds ago, who in danger of his life had performed that marvelous trick of jiu-jutsu, had followed his unknown assailant into that dark, mysterious house, from no single window of which was a single gleam of light visible.  Tavernake had led an uneventful life.  Of the passions which breed murder and the desire to kill he knew nothing.  He was dazed with the suddenness of it all.  How could such a thing happen in the midst of London, in a thoroughfare only momentarily deserted, at the further end of which, indeed, were many signs of life!  Then the thought of that knife made him shiver—­blue glittering steel cutting the air like whipcord.  He remembered the look in the assassin’s face—­ horrible, an epitome of the passions, which seemed to reveal to him in that moment the existence of some other, some unknown world, about which he had neither read nor dreamed.

The sound of footsteps came as an immense relief.  A man came round the corner, smoking a cigarette and humming softly to himself.  The presence of another human being seemed suddenly to bring Tavernake’s feet back upon the earth.  He moved toward the pavement and addressed the newcomer.

“Can you tell me how to get inside that house?” he asked quickly.

The man removed the cigarette from his mouth and stared at his questioner.

“I should ring the bell,” he replied, “but surely it’s unoccupied?  What do you want to get in there for?”

“Less than a minute ago,” Tavernake told him, “I was walking here with a friend.  A man came up behind us and tried deliberately to stab him.  He bolted afterwards through that door, my friend followed him, the door was closed in my face.”