“I believe I have, vaguely,” replied Robin. “Isn’t it something to do with a motor engine?”

“No,” said Bruce. “It’s an extraordinary invention which absolutely suppresses the noise of the discharge of a gun.”

Robin shot a quick glance at the speaker.

“Go on,” he said.

“It’s a marvelous thing, really,” the boy continued, warming to his theme. “A man at Havre had one when I was at the base there, during the war. It’s a little cup-shaped steel fitting that goes over the barrel. You can fire a rifle fitted with one of these silencers in a small room and it makes no more noise than a fairly loud sneeze ...”

“Ah!”

Robin was listening intently now.

“Parrish had a Maxim silencer,” Bruce went on impressively.

Parrish had?”

“It was fitted on his automatic pistol, the one he had in his hand when they found him ...”