He stared at his secretary through his spectacles, as though he had seen him that morning for the first time for many months. “Yes, I think we both need a change of occupation,” he continued. “I feel that I should welcome some enticing problem, mathematical or human. It is time we stepped from our recent absorption back into the world. Let me see. What is the date?”

“April 28th, sir,” replied Harold with a smile. He knew well enough that the Professor would have accepted any other day he chose to mention.

“Dear me! Then the world is six months older than when we retired from it. No doubt many interesting problems have arisen in the interval, but I fear that their solutions lie in other hands than ours. By the way, when does our friend Inspector Hanslet return from America?”

Harold turned to one of the big presses which lined the walls of the room, and took from it a folder marked “Inspector Hanslet.” He consulted this for a moment, then looked up towards his employer. “At the end of this month, sir. There is no definite date mentioned. I dare say he is in London already.”