“Except Mr. Sherlock Holmes,” said my companion, with a somewhat bitter smile. “Well, let us hear about it. What sort of a job did you make of it?”

“I must ask you first, Mr. Holmes, to glance at this rough plan, which will give you a general idea of the position of the professor’s study and the various points of the case. It will help you in following my investigation.”

He unfolded the rough chart, which I here reproduce, and he laid it across Holmes’s knee. I rose and, standing behind Holmes, studied it over his shoulder.