Mayfield was in darkness when the cab drove up to the gate. Carver sprang out, ran across the concrete yard and up the steps to the door with Tab at his heels. He flashed a pocket lamp upon the keyhole, flung the door wide open, as the second cab drew up at the gate to discharge half-a-dozen police officers in various stages of attire. The hall was in darkness, but they had the lights on in a second and Carver ran into the sitting-room. The door leading to the vault was open. “Oh!” said Carver thoughtfully. He came back to give instructions to his posse and then, followed by Tab, he went down the stone steps, and along the corridor. The door of the vault was closed and locked and the room was unlighted. Carver felt in his pocket, took out the duplicate key, that upon which Walters had worked so industriously and snapped back the lock. At touch from his thumb and the vault was flooded with light. He paused in the open doorway and looked. Wellington Brown was lying face downward in the centre of the room, blood was flowing from under him, _and on the table, in the exact centre, was the key of the vault_! Carver picked it up. There was no doubt about it; the old blood-stain was still upon it and he looked blankly at his companion. “Well, what do you think of that, Tab,” he asked in a hushed voice. Tab did not reply. He was standing just inside the doorway looking down at his feet, and between his feet was something, the sight of which deprived him of speech. He stooped slowly and picked it up, laying it upon the palm of his hand. “Another new pin!” said the detective thoughtfully. “This time, inside!” A thorough search of the house failed to discover the second man. He must have made his escape just before the police arrived, for the smoke of the pistol’s explosion still hung in the vaulted roof. When the doctors came and the body was moved Tab spoke what was in his mind. “Carver, I have been a fool,” he said quietly. “We ought to have been able to prevent this. We should have done it if I had only remembered.” “What?” asked Carver, arousing himself from thoughts which did not seem to be particularly pleasant, to judge from his expression. “That key was in Rex’s box. I remember now that he mentioned casually that he put it in his trunk before he went away.” Carver nodded. “I guessed that,” he said. “Probably we both arrived at that solution when we saw the key on the table. The burglary of your flat is, of course, explained. He came the first time for the key and was disturbed by the tenant from the flat beneath and got away before it had been found. Tonight, the need being urgent, he took a chance, found the key, and--” he shrugged. “How did the key get on the table? The door was locked both sides, yet there is the key--and the new pin,” he added half to himself, “the second new pin.” He got up and stretched himself and began to pace up and down old Trasmere’s sitting-room.