"But Peggy's belated admissions did more than suggest that Penreath was the victim of a sinister plot--they narrowed down the range of persons by whom it could have been contrived. The plotter was not only an inmate of the inn, but somebody who had seen the match box and knew that it belonged to Penreath. "I returned to Flegne to resume the investigations I had broken off nearly three weeks before, and from that point my discoveries were very rapid, all tending to throw suspicion on Benson. The first indication was the outcome of a remark of mine about his height, and the broken gas light in Mr. Glenthorpe's bedroom. It was purely a chance shot, but it threw him into a pitiable state of excitement. I let him think, however, that it was nothing more than a chance remark. That night I was put to sleep in Penreath's room, and there I made two discoveries. The first was the existence of a small door, behind the wardrobe, opening on a corresponding door on the other side, which in its turn opens into Mr. Glenthorpe's room. Thus it would be possible for a person in the room Penreath occupied, discovering these doors as I did, to see into the next bedroom--under certain conditions. My second discovery was the outcome of my first discovery--I picked up underneath the wardrobe a fragment of an appealing letter which Penreath had commenced to write to his fiancee, and had subsequently torn up. It was a long time before I grasped the full significance of these two discoveries. Why should a man, after writing a letter of appeal to his fiancee, decide not to send it and destroy it? The most probable reason was that something had happened to cause him to change his mind. What could have happened to change the conditions so quickly? The hidden doors in the wall, which looked into the next room, supplied an answer to the question. Penreath had looked through, and seen--what? My first thought was that he had seen the murder committed, but that theory did not account for the destruction of the letter, and his silence when arrested, unless, indeed, the girl had committed the murder. The girl--Peggy! It came to me like a flash, the solution of the strangest aspect of this puzzling case--the reason why Penreath maintained his dogged silence under an accusation of murder.