“I have,” he said. “There is a curious sensation of heat in the place.”

“Ah!” exclaimed the other, with a slight start. “You have noticed it. This unaccountable heat⁠—”

“But its cause, I gather, is not in the house itself⁠—but outside,” I was astonished to hear the doctor add.

Colonel Wragge rose from his chair and turned to unhook a framed map that hung upon the wall. I got the impression that the movement was made with the deliberate purpose of concealing his face.

“Your diagnosis, I believe, is amazingly accurate,” he said after a moment, turning round with the map in his hands. “Though, of course, I can have no idea how you should guess⁠—”