“At that very moment, if you remember, Constable Fiske had just crossed the foot-bridge, and was walking towards the Harrow Road, and he was quite sure (for he was closely questioned afterwards) that no one overtook him from behind. Now there would be no way of getting from one side of the canal to the other at this point except over that foot-bridge; the nearest bridge is fully two hundred yards further down the Blomfield Road. The girl was alive a minute _before_ the constable crossed the foot-bridge, and it would have been absolutely impossible for any one to have murdered a girl, placed the knife in her hand, run a couple of hundred yards to the next bridge and another three hundred to the corner of Harrow Road, all in the space of three minutes. “This _alibi_, therefore, absolutely cleared Dr. Stapylton from any suspicion of having murdered Miss Elliott. And yet, looking on that man as he sat there, calm, cool and contemptuous, no one could have had the slightest doubt but that he was lying—lying when he said he had not seen Miss Elliott that evening; lying when he denied Dr. Earnshaw’s statement; lying when he professed himself ignorant of the poor girl’s fate. “Dr. Earnshaw repeated his statement with the same emphasis, but it was one man’s word against another’s, and as Dr. Stapylton was so glaringly innocent of the actual murder, there seemed no valid reason at all why he should have denied having seen her that night, and the point was allowed to drop. As for Nurse Dawson’s story of his alleged quarrel with Miss Elliott on the Saturday night, Dr. Stapylton again had a simple and logical explanation. “‘People who listen at keyholes,’ he said quietly, ‘are apt to hear only fragments of conversation, and often mistake ordinary loud voices for quarrels. As a matter of fact, Miss Elliott and I were discussing the dismissal of certain nurses from the Home, whom she deemed incompetent. Nurse Dawson was among that number. She desired their immediate dismissal, and I tried to pacify her. That was the subject of my conversation with the deceased lady. I can swear to every word of it.’” Chapter IV The man in the corner had long ceased speaking, and was placing quietly before me a number of photographs. One by one I saw the series of faces which had been watched so eagerly in the coroner’s court that memorable afternoon by an excited crowd. “So the fate of poor Miss Elliott has remained wrapt in mystery?” I said thoughtfully at last. “To every one,” rejoined the funny creature, “except to me.” “Ah! What is your theory, then?” “A simple one, dear lady: so simple that it really amazes me, that no one, not even you, my faithful pupil, ever thought of it.” “It may be so simple that it becomes idiotic,” I retorted with lofty disdain. “Well, that may be. Shall I at any rate try to make it clear.” “If you like.”