“I thought I would come round, on the chance that you had some hint to give me,” replied Hanslet. “I can’t make head or tail of the business I told you about last night. The more I think about it, the more puzzling it seems. It’s the utter lack of motive that makes it all so inexplicable.”

“I believe, mind, I say only that I believe, that I have discovered the motive,” said the Professor quietly.

“You have!” exclaimed Hanslet excitedly. Then, seeing the slow movement of the Professor’s head, he smiled. “I know you won’t tell me until you are certain,” he continued. “But at least tell me this. Are there likely to be any more of these mysterious deaths?”

“There will be one more, unless I am able to prevent it,” replied the Professor.