"Ah, I've no doubt. Do you happen to have the key with you?"
"It's on the bunch hanging up in my box, sir. Shall I fetch it?"
"I should like to see it, if you will."
The housekeeper disappeared, and presently returned with a large bunch of keys.
"This is the one, Mr. Hewitt," he explained, lifting it from among the rest.
Hewitt examined it closely, and then placed beside it one from the bunch Plummer had given him. "It seems you're not the only person who ever had a key exactly like that, Hutt," he said, "See here—this was found in Mr. Denson's pocket."
Plummer nodded sagaciously. "All in the plant," he said. "See—it's brand new; clean as a new pin, and file marks still on it."
"Take us to this back door, Hutt," Hewitt pursued. "We'll try this key. Is there a back staircase?"
There was a small back staircase, leading to the coal-cellars, and only used by servants. Down this we all went, and on a lower landing we stopped before a small door. Hewitt slipped the key in the lock and turned it. The door opened easily, and there before us was the little courtyard which I think I have mentioned in one of my other narra-
