“I next examined the motive for the call. That was difficult. I could only get at it by judging its result . Which was⁠—that the murder was discovered that night instead of⁠—in all probability⁠—the following morning. You agree with that?”

“Ye‑es,” I admitted. “Yes. As you say, Mr. Ackroyd, having given orders that he was not to be disturbed, nobody would have been likely to go to the study that night.”