The doctors had certified that the wound could not have been self-inflicted, while there was plenty of evidence to show that there had not been a struggle.

From the fact that the front-door was locked, and that the key was in the murdered man's pocket, it was certain that the assassin must have left the house by the back.

There was one question, however, so trivial in itself that one might have been excused for not taking note of it, that attracted my attention.

As I have said, the old man had been stabbed from behind, and when he was discovered by the police next day, his overturned chair was lying beside him.

This, to my mind, showed that he had been seated with his back to the door when the crime had been perpetrated.