How had Harvey Froyant been killed? His desk was opposite the fire-place, and the desk was a narrow Jacobean affair which would have distracted any ordinary man by its lack of width, but it was a favourite of the dead financier. From which way had the murderer approached him? From behind? The knife was thrust in a downward direction, and the theory that his assailant came upon him unawares was at least plausible. But why the glove? Inspector Parr handled it gingerly. It was a leather gauntlet, such as a chauffeur uses, and had been well worn. His next move was to call the Police Commissioner and, as he had suspected, the colonel was waiting for a communication from Harvey Froyant. “Then he did not telephone to you?” “No. What has happened?” Parr told him briefly, and listened unmoved to the almost incoherent fury of his chief at the other end of the wire. Presently he hung up the receiver and went back to the hall, to find his men already posted. “I am searching every room in the house,” he said. He was gone half an hour, and returned to Derrick Yale. “Well?” asked Yale eagerly. Parr shook his head. “Nothing,” he said. “There is nobody here who has no right to be here.” “How did they get into the room? The hall-way was never empty except when Steere came into the drawing-room.” “There may be a trap in the floor,” suggested Yale. “There are no traps in drawing-room floors in the West End of London,” snapped Parr, but a further search had a surprising result. Turning up one corner of the carpet, a small trap-door was discovered, and the butler explained that in the days of the war, when air raids were a nightly occurrence, Mr. Froyant had had a bomb-proof shelter constructed of concrete in a lower wine cellar, ingress to which was gained by means of a flight of stairs leading from his study. Parr went down the stairs with a lighted candle and discovered himself in a small, square, cell-like room. There was a door, which was locked, but, searching the body of Harvey Froyant, they found a master key. Beyond the first door was a second of steel and this brought them into the open. The houses in the street shared a common strip of lawn and shrubbery. “It is quite possible to get into here through the gate at the end of the garden,” said Yale, “and I should say that the murderer came this way.” He was flashing his electric lamp along the ground. Suddenly he went down on to the ground and peered. “Here is a recent footprint,” he said, “and a woman’s!” Parr looked over his shoulder. “I don’t think there is any doubt about that,” he said. “It is recent.” And then suddenly he stepped back. “My God!” he gasped in awe-stricken tones. “What a devilish plot!” For it came upon him with a rush that this was the footprint of Thalia Drummond. Chapter XXXI. Thalia Answers a Few Questions