"Then we may get some interesting reactions," responded Hemingway. "Come on! We'll take the knife back to headquarters, and get a bit of dinner at the same time. I want to think."
He was unusually silent during the hot and substantial meal provided by the cook at the Blue Dog inn; and the Sergeant, respecting his preoccupation, made no attempt to converse with him. Only when the cheese was set before them did he venture to say: "I've been thinking about that weapon."
"I haven't," said Hemingway. "I've been thinking about that locked door."
"I don't seem to get any ideas about that," confessed the Sergeant, "The more I think about it the more senseless it seems."
"There must have been a reason for it," said Hemingway. "A pretty strong one, too. Whoever murdered Nathaniel Herriard, and locked the door behind him, was taking the hell of a chance of being caught in the act. He didn't do it for fun."
"No," agreed the Sergeant, thinking it over. "It looks as though you're right there. But what reason could he possibly have had?"
Hemingway did not answer. After a few moments, the Sergeant said slowly: "Supposing the murdered man didn't lock the door himself, in the first place? We've no proof that he did, after all. I was just wondering… If the murderer walked into the room, and locked the door behind him -"
"Old Herriard would have kicked up a rumpus."
"Not if it had been his nephew he wouldn't. He might have thought Stephen wanted to have a straight talk with him, without the valet's coming in to interrupt them."
"Well?" said Hemingway, showing a faint interest.