“That’s so,” replied Day. “The watchman on duty between twelve midnight and seven a. m. is always relieved by a Mrs. Turner—she sweeps and cleans the place up generally. When she arrived she got no answer, of course. Couldn’t get in! So she got into touch with the people next door, who ’phoned me. I came down post-haste. I guessed there was trouble because I knew we had some valuable things here.” Goodall pursed his lips. “The door of your office was locked when you arrived?” Day knitted his brows. Then a sudden flush of color welled and broke into the ordinary paleness of his face. “Inspector,” he said, “write me down a dunderhead. The door of my office was closed but not locked. I remember it distinctly now. I brought the keys of the front door along—my own keys—we all came in together—my partners and I—we found poor Mason on the floor there and I rushed to the ’phone for you and Doctor Archer. I never gave a thought to the fact that the door of my office wasn’t locked. The idea of the murder drove it completely from my mind.” He paused—a little crestfallen and apologetic. Goodall turned to the group of listeners somewhat dramatically. “That’s how the murderer got in and managed the job,” he declared. “Got in while the attention of the two watchmen was being distracted by the woman ‘decoy’—made his way quickly up here—picked the lock of that door”—he pointed to the door of the private office—“hid in the office till the time came for action—then pounced on Mason from behind.” Linnell interposed. “Would he have sufficient time, do you think, Inspector, to pick the lock before Mason and Druce could get up here?” “Depends on Mason and Druce and the time they spent downstairs,” replied Goodall. He swung round like lightning on the man concerned. Druce reddened. “How long were you before you and Mason came upstairs?” Druce shifted his feet uneasily. “Not more than a matter of a few minutes, sir. Say five minutes!” Goodall flashed a look of understanding at him. “I suppose you stayed at the foot of the staircase for a ‘few draws,’ eh?” He turned on his heel to Mr. Day. “Smoking forbidden here during the watchmen’s shifts, Mr. Day?” Day inclined his head in assent. “Thought so. Well, Druce, am I right?” “Well, sir, Mason certainly did have a puff or two—only for a few minutes though.” “Why did you come back with him—upstairs again—when you were going home?” “For my things, sir. I never collected ’em together when I ’eard ’im knock. I always went straight down to ’im.” Goodall nodded. “You and Mason were certainly long enough absent from the room to give this fellow his chance and Mason paid for his mistake with his life, poor chap. Now—about this woman, Druce—what was she like? Describe her!” Druce shook his head with evident misgiving. “I’m afraid I can’t ’elp you much there, sir. I ain’t much of a ’and at descriptions—my daughter Poppy now—if she were ’ere she’d be able to——”