There was a considerable pause. A flush had slowly mounted Swayne’s face, and it was only with an obvious effort that he controlled himself. Once he looked toward Black, who had been a silent witness of the interview.
“Well, after those first two incidents,” Swayne went on at last, “the door of Mr. Carroll’s private office was always locked on the inside the moment he was left alone. Now I am not a fool, Professor Van Dusen. In my mind it stands to reason that if Mr. Carroll disappeared from that room twice when the door was left unlocked, he is gone from it practically all the time when the door is locked; therefore —”
“Opinion again,” interrupted The Thinking Machine curtly. “Facts, Mr. Swayne, facts!”
“If he isn’t gone, why does he keep the door locked?”
“Perhaps,” and the crabbed l
