“And the time?”

“He certainly will,” Mattern said, laughing, “because we were discussing the accuracy of watches. I bet him that my own wrist watch wouldn’t vary more than one second in half an hour from his standard chronometer. I was there half an hour, and we checked the second hand.”

“That brings you up to two-thirty,” Mason said.

“That’s right.”

“What did you do after two-thirty, Mattern?”

“I had some matters to go over with the accountant who makes out Mr. Tidings’ income tax reports. I asked him to meet me at the office at quarter of three. We were there until five.”

“And after five?” Mason inquired.

“I invited a young lady to meet me at five-twenty, to go to dinner and a movie.”

“The same young lady whom you took to lunch?”

“No, another one.”