"Who would unlock it?" replied Musard. "The inference, in view of what has happened, seems rather that the door was unlocked to-day, and Tufnell stumbled upon the fact by a lucky chance--by Fate, if you like. At least it looks like that to me." "And the murderer entered by the door?" "Yes." "I think that is assuming too much," said Caldew. He had no intention of pointing out to his companion that such an assumption overlooked the fact that Tufnell's discovery, and the locking of the door, had not prevented the crime and the subsequent escape of the murderer. He turned to leave the room, but Musard was in a talkative mood. He offered the detective a cigar, and kept him for a while, chatting discursively. Caldew was in no humour to listen. His mind was full of the problems of this strange case, and he was anxious to return upstairs. He took the first opportunity of terminating the conversation and leaving the room. It was his intention to conceal himself in one of the wardrobes of the bedroom in the hope that the owner of the trinket he had found would return in search of it. As he reached the landing he was surprised to see that the door of the murdered woman's bedroom was wide open, although he remembered distinctly that he had closed it when he left the room to accompany the butler downstairs. With a quickly beating heart he hurried across the room to the spot where he had left the trinket. But it was gone. CHAPTER VII It was the morning after the murder, and five men were seated in the moat-house library. One of them attracted instant attention by reason of his overpowering personality. He was a giant in stature and build, with a massive head, a large red face from which a pair of little bloodshot eyes stared out truculently, and a bull neck which was several shades deeper in colour than his face. He was Superintendent Merrington, a noted executive officer of New Scotland Yard, whose handling of the most important spy case tried in London during the war had brought forth from a gracious sovereign the inevitable Order of the British Empire. Merrington was known as a detective in every capital in Europe, and because of his wide knowledge of European criminals had more than once acted as the bodyguard of Royalty on continental tours, and had received from Royal hands the diamond pin which now adorned the spotted silk tie encircling his fat purple neck.