Standing on one of the walls was the figure of a man, gun in hand. Moe recognized him immediately: the Special Investigator to the District Attorney’s office. He flung himself flat as Conrad shot at him again.

Blood was running down Moe’s sleeve and down his fingers. He felt a dull burning pain in his right shoulder. He looked along the path, but the girl had now vanished, and he drew back his lips in a snarl of fury.

Conrad was about fifteen yards from where Moe crouched. Two paths divided him from the path in which Moe was. He couldn’t see him now, but he knew he was still there. The wall was only six inches thick and it wasn’t easy to stand on it, let alone jump the six feet to the next wall.

Already a dozen police were climbing up on to the top of the walls and were spreading out slowly to surround the maze.

“He’s here,” Conrad shouted, and pointed to the path where Moe was crouching.

Moe straightened up and fired at Conrad, who felt the slug zip past his face. As he automatically ducked, he lost his balance and fell into one of the mirrored paths.

The police had called for planks and were crossing the paths by laying the planks across the tops of the walls, and then pulling the planks after them.

But by the time they reached the path where Moe had been, he had vanished, leaving only a smear of blood on one of the mirrors to show where he had been.

A police sergeant, squatting on the wall, looked down at Conrad.

“You all right, sir?”