“In the meantime the housekeeper had also arrived upon the scene, but she was just too late to catch the young man’s dying words. Leaving Susan with the body, she hurried to the professor’s room. He was sitting up in bed, horribly agitated, for he had heard enough to convince him that something terrible had occurred. Mrs. Marker is prepared to swear that the professor was still in his night-clothes, and indeed it was impossible for him to dress without the help of Mortimer, whose orders were to come at twelve o’clock. The professor declares that he heard the distant cry, but that he knows nothing more. He can give no explanation of the young man’s last words, ‘The professor - it was she,’ but imagines that they were the outcome of delirium. He believes that Willoughby Smith had not an enemy in the world, and can give no reason for the crime. His first action was to send Mortimer, the gardener, for the local police. A little later the chief constable sent for me. Nothing was moved before I got there, and strict orders were given that no one should walk upon the paths leading to the house. It was a splendid chance of putting your theories into practice, Mr. Sherlock Holmes. There was really nothing wanting.”

“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.

“It is very rough, of course, and it only deals with the points which seem to me to be essential. All the rest you will see later for yourself. Now, first of all, presuming that the assassin entered the house, how did he or she come in? Undoubtedly by the garden path and the back door, from which there is direct access to the study. Any other way would have been exceedingly complicated. The escape must have also been made along that line, for of the two other exits from the room one was blocked by Susan as she ran downstairs and the other leads straight to the professor’s bedroom. I therefore directed my attention at once to the garden path, which was saturated with recent rain, and would certainly show any footmarks.

“My examination showed me that I was dealing with a cautious and expert criminal. No footmarks were to be found on the path. There could be no question, however, that someone had passed along the grass border which lines the path, and that he had done so in order to avoid leaving a track. I could not find anything in the nature of a distinct impression, but the grass was trodden down, and someone had undoubtedly passed. It could only have been the murderer, since neither the gardener nor anyone else had been there that morning, and the rain had only begun during the night.”

“One moment,” said Holmes. “Where does this path lead to?”

“To the road.”

“How long is it?”

“A hundred yards or so.”

“At the point where the path passes through the gate, you could surely pick up the tracks?”

“Unfortunately, the path was tiled at that point.”

“Well, on the road itself?”

“No, it was all trodden into mire.”

“Tut-tut! Well, then, these tracks upon the grass, were they coming or going?”

“It was impossible to say. There was never any outline.”

“A large foot or a small?”

“You could not distinguish.”

Holmes gave an ejaculation of impatience.