Gimblet put the letter away with the other items of evidence of Mark's guilt: the telegram from the analyst in Edinburgh, the measurements of the footprints on the rose-bed, and of those other marks near the hedge by which he had at first been mystified. It was another thread in the thin cord that, like the silken line Ariadne gave to Theseus, had led him to come successfully out of the bewildering labyrinth into which the investigation of the crime had beguiled him. CHAPTER XXII It was after dinner that night, as he sat in the little drawing-room of the cottage with Lady Ruth and Sir Arthur, that his hostess asked him to explain to them how he had contrived to detect the way in which the murder had been committed. "You promised to tell me all about it," Lady Ruth reminded him, "if I would keep silent about your finding the papers in the statue." "Tell us the whole thing from the beginning," Sir Arthur urged him. "I will willingly tell you anything that may interest you," Gimblet consented readily. "Every one enjoys talking about their work to sympathetic listeners such as yourselves. It is a bad thing to start on a case with a preconceived idea, and I can't deny that when I first came here I was very near having an _idee fixe_ as to the origin of the crime. I tried to deceive myself into thinking that I kept an open mind on the subject; but I don't think I ever really doubted for a minute that the Nihilist society to which Lord Ashiel had formerly belonged was responsible for the murder. Even after my conversation with the new peer, which showed me that things looked blacker against Sir David Southern than I had expected, I was far from convinced that he was guilty, though I was obliged to admit that there was some ground for the conclusion come to by the police. "But what was the evidence against him? Sir David was known to have quarrelled with his uncle; he had even been heard to say he had a good mind to shoot him. But that was more than twenty-four hours previous to the crime, and the words were uttered in a moment of anger, when he probably said the first thing that came into his head. Was he likely to have hugged his rage in silence for the hours that followed, and then to have walked out into the garden and shot his uncle in cold blood and without further warning? It did not appear to me probable, but then I did not know the young man. "He was not to be found when the deed was discovered, and a hunt instituted for the murderer. Well, he had an answer to that which fitted in with my own theory. He said he saw some one hanging about the grounds, and went to look for him. But it was said that the night was so dark as to make it improbable that anyone should have been seen, even if there had been anyone to see. That cut both ways, to my mind. For it would account for the intruder making his escape undiscovered.