Then suddenly he was struck violently. By nothing! A vast weight, it seemed, leapt upon him, and he was hurled headlong down the staircase, with a grip on his throat and a knee in his groin. An invisible foot trod on his back, a ghostly patter passed downstairs, he heard the two police officers in the hall shout and run, and the front door of the house slammed violently.

He rolled over and sat up staring. He saw, staggering down the staircase, Kemp, dusty and disheveled, one side of his face white from a blow, his lip bleeding, and a pink dressing-gown and some underclothing held in his arms.

"My God!" cried Kemp, "the game's up! He's gone!"