Shelley looked up at it with some concern. He had brought an automatic pistol with him, but he did not want to use it if its use could possibly be avoided. Yet there was no getting away from the fact that the man they were after was a double murderer, who would not hesitate to kill again if he thought that his ends could best be achieved by such means.

Shelley pondered the problem for a moment with wrinkled brow. The others looked at him, eager to do something but waiting for a lead from him before they decided what that “something” could be.

“The straightforward way seems the best,” said Shelley.

“Okay, sir,” answered Cunningham, and marched to the door of Blackdown House. Seizing the gnarled old knocker with his right hand, he banged it resolutely two or three times, arousing resounding echoes in the old house. Then they all waited for the result.

There was no result. The house stared at them solemnly, as if defying them to do their worst. But there was certainly no reply.

“Who lives here, Cartwright?” asked Shelley. “Do you happen to know?”

“Ay.”

“Well, who is it?”

“A fellow called Ramsbottom. He’s lived here for years and years.”

“Is he often away from home?”

Cartwright shook his head sadly. “Can’t say as I’ve ever heard of him leaving Penistone in his life,” he said.

Shelley was disappointed. He had hoped that this was their goal at last, but the outlook, which had been quite promising, suddenly took on a more sinister appearance. It might be that they were climbing up the wrong tree after all. He tried not to feel too pessimistic about the whole affair, but he tried in vain. Then—quite suddenly—another thought came into his mind.

“Has he got a beard?”’ he asked.

“Ay,” answered Cartwright, and Shelley’s heart sang again.

“Try again, Cunningham,” he ordered, and Cunningham obeyed. He gave a perfect fusillade of knocks, awaking all the nooks and corners of the place, until housewives in other houses down the street threw open doors and poked inquisitive noses out of bedroom windows to see what was amiss. Still there was no reply. The house might have been an abode of the dead.

“Once more,” said Shelley grimly, and Cunningham willingly complied.

This time there was some response. Shelley was watching the mysterious house with great care, and he saw a flutter of a window-blind in one of the rooms in the top story. It was the merest movement, and to a less observant eye it would doubtless have passed unnoticed. Not so with Shelley. He missed nothing.

“There’s someone in,” he announced. “Watch that blind up there, Cunningham. There it goes again!” And certainly the blind had been lifted the smallest fraction of an inch, as if someone inside had endeavoured to peer out to see who was disturbing the peace of this still somnolent street.