"I'm dead sure of it. While Ernest is strolling back to the house, he comes back cautiously to the gate. If he'd made up his mind, as he must have, to kill Ernest, he didn't open that gate till Ernest had reached the house again, which was at 10.00 p.m. He wouldn't have run the risk of Ernest hearing him. No point in it. Does he stride up the path bold as brass, thus advertising his presence? Of course he doesn't! He creeps up, and if it takes a minute to reach the study from that gate, walking ordinarily, as we know it does, it's my belief it took X a sight longer to do it in the dark, treading warily. By the time he's in the study again it must be a couple of minutes after 10.00, at which time, mark you, Glass saw him coming out of the garden-gate."
"I'm afraid you've got a fixation, Skipper," said Hannasyde gently. "We don't know that X was the murderer."
The Sergeant swallowed this, replying with dignity: "I was coming to that. It could have been Budd, come back secretly, and lying in wait in the garden till the coast was clear; or it could have been Mr. North. But if X, whom Glass saw, was Charlie Carpenter, what was he doing while Ernest was being knocked on the head?"
"There's another possibility," said Hannasyde. "Suppose that North was the murderer -'
"Just a moment, Super! Is North X?" demanded Hemingway.
"Nobody is X. Assuming that North was the man Mrs. North saw coming up the path, we have to consider the possibility of Fletcher's having been killed at any time between 9.45 and 10.01."
The Sergeant blinked. "Mrs. North's revised version being so much eye-wash? Where does Carpenter come in?"
"After the murder," replied Hannasyde.
There was a short pause. "We've got to find Carpenter," announced the Sergeant.
"Of course. Have you got anyone on to that?"