"And if they were not, no one would enter there," put in Dan quickly. "Outside is a walled garden, and the wall is very high with broken bottles on top. I suppose, Mr. Durwin, you are thinking that some one may have come in to kill Sir Charles between the time of Mrs. Brown's departure and your coming?" "Yes," assented the other sharply, "if the perfume is a clue, Mrs. Brown must be innocent. Penn, as we know from the statement of the typewriter girl, was in his room all the time, and the servants have fully accounted for themselves. We examined them all--the Inspector and I did, that is--when you were at the theatre," he waved his hand with a shrug. "Who can say who is guilty?" "Well," said Tenson, snapping the elastic band round his note-book and putting it into his pocket, "we have the evidence of the fly and of the perfume." "What do you think about the fly?" asked Dan, staring. "I don't know what to think. It is an artificial fly, exquisitely made and has been gummed on the dead man's neck behind the left ear. The assassin must have placed it there, since a man would scarcely do such a silly thing himself. Why, it was placed there I can't say, any more than I can guess why Sir Charles was murdered, or who murdered him. The affair is a complete mystery, as you must admit." Before the inquest and after the inquest, more people than the three men who had held the discussion in the presence of the dead, admitted that the affair was a mystery. In fact the evidence at the inquest only plunged the matter into deeper gloom. Tenson, acting on Durwin's advice, sought the office of the tramp-steamer company--The Universal Carrier Line--in which the late Sir Charles was chief shareholder and director, to learn without any difficulty the whereabouts of Mrs. Brown, the mother of the drowned man. She proved to be an entirely different person to the woman who had given the name on the fatal night, being lean instead of stout, comparatively young instead of old, and rather handsome in an elderly way in place of being wrinkled and worn with grief. She declared that she had never been near Moon's house on the night of the murder, or on any other night. Mrs. Bolstreath, Lillian, the footman, and Dan all swore that she was not the Mrs. Brown who had sought the interview with Sir Charles. Therefore it was argued by every one that Mrs. Brown, taking a false name and telling a false story, must have come to see Moon with the deliberate intention of murdering him. Search was made for her, but she could not be found. From the moment she passed out of the front door she had vanished, and although a description was published of her appearance, and a reward was offered for her apprehension no one came forward to claim it. Guilty or innocent, she was invisible.