The thing for a man who has spent many hours within four walls, Labar decided, was a good brisk walk. He parted from Malone under the blue lamp at the entrance to the police station, and paused to light a cigarette. He nodded amiably to the constable on reserve duty at the doorway, and setting his face towards Chelsea where his modest bachelor apartments were located, swung off briskly down the little courtyard that leads from Grape Street to Piccadilly.

He had taken not more than a score of strides when some sixth sense impelled him to whirl upon his heels. In that fraction of a second he had an impression of a dark figure hurling itself upon him from a doorway. An instant earlier and he had saved himself. As it was, he flung up an arm, almost by instinct, and broke the impact of a sandbag. Nevertheless, he went down half-stunned and feebly grappling with his opponent.