Old Bond Street presented a gloomy and deserted prospect to Chief Inspector Kerry as he turned out of Piccadilly and swung along toward the premises of Kazmah. He glanced at the names on some of the shop windows as he passed, and wondered if the furriers, jewelers and other merchants dealing in costly wares properly appreciated the services of the Metropolitan Police Force. He thought of the peacefully slumbering tradesmen in their suburban homes, the safety of their stocks wholly dependent upon the vigilance of that Unsleeping Eye—for to an unsleeping eye he mentally compared the service of which he was a member.  
A constable stood on duty before the door of the block. Red Kerry was known by sight and reputation to every member of the force, and the constable saluted as the celebrated Chief Inspector appeared.
 
“Anything to report, constable?”
 
“Yes, sir.”
 
“What?”
 
“The ambulance has been for the body, and another gentleman has been.”
 
Kerry stared at the man.
 
“Another gentleman? Who the devil's the other gentleman?”
 
“I don't know, sir. He came with Inspector Whiteleaf, and was inside for nearly an hour.”
 
“Inspector Whiteleaf is off duty. What time was this?”
 
“Twelve-thirty, sir.”
 
Kerry chewed reflectively ere nodding to the man and passing on.
 
“Another gentleman!” he muttered, entering the hallway. “Why didn't Inspector Warley report this? Who the devil—” Deep in thought he walked upstairs, finding his way by the light of the pocket torch which he carried. A second constable was on duty at Kazmah's door. He saluted.
 
“Anything to report?” rapped Kerry.
 
“Yes, sir. The body has been removed, and the gentleman with Inspector—”
 
“Damn that for a tale! Describe this gentleman.”
 
“Rather tall, pale, dark, clean-shaven. Wore a fur-collared overcoat, collar turned up. He was accompanied by Inspector Whiteleaf.”
 
“H'm. Anything else?”
 
“Yes. About an hour ago I heard a noise on the next floor—”
 
“Eh!” snapped Kerry, and shone the light suddenly into the man's face so that he blinked furiously.
 
“Eh? What kind of noise?”
 
“Very slight. Like something moving.”
 
“Like something! Like what thing? A cat or an elephant?”
 
“More like, say, a box or a piece of furniture.”
 
“And you did—what?”
 
“I went up to the top landing and listened.”
 
“What did you hear?”
 
“Nothing at all.”
 
Chief Inspector Kerry chewed audibly.
 
“All quiet?” he snapped.
 
“Absolutely. But I'm certain I heard something all the same.”
 
“How long had Inspector Whiteleaf and this dark horse in the fur coat been gone at the time you heard the noise?”
 
“About half an hour, sir.”
 
“Do you think the noise came from the landing or from one of the offices above?”
 
“An office I should say. It was very dim.”
 
Chief Inspector Kerry pushed upon the broken door, and walked into the rooms of Kazmah. Flashing the ray of his torch on the wall, he found the switch and snapped up the lights. He removed his overall and tossed it on a divan with his cane. Then, tilting his bowler further forward, he thrust his hands into his reefer pockets, and stood staring toward the door, beyond which lay the room of the murder, in darkness.
 
“Who is he?” he muttered. “What's it mean?”
 
Taking up the torch, he walked through and turned on the lights in the inner rooms. For a long time he stood staring at the little square window low down behind the ebony chair, striving to imagine uses for it as his wife had urged him to do. The globular green lamp in the second apartment was worked by three switches situated in the inside room, and he had discovered that in this way the visitor who came to consult Kazmah was treated to the illusion of a gradually falling darkness. Then, the door in the first partition being opened, whoever sat in the ebony chair would become visible by the gradual uncovering of a light situated above the chair. On this light being covered again the figure would apparently fade away.
 
It was ingenious, and, so far, quite clear. But two things badly puzzled the inquirer; the little window down behind the chair, and the fact that all the arrangements for raising and lowering the lights were situated not in the narrow chamber in which Kazmah's chair stood, and in which Sir Lucien had been found, but in the room behind it—the room with which the little window communicated.
 
The table upon which the telephone rested was set immediately under this mysterious window, the window was provided with a green blind, and the switchboard controlling the complicated lighting scheme was also within reach of anyone seated at the table.
 
Kerry rolled mint gum from side to side of his mouth, and absently tried the handle of the door opening out from this interior room—evidently the office of the establishment—into the corridor. He knew it to be locked. Turning, he walked through the suite and out on to the landing, passing the constable and going upstairs to the top floor, torch in hand.
 
From the main landing he walked along the narrow corridor until he stood at the head of the back stairs. The door nearest to him bore the name: “Cubanis Cigarette Company.” He tried the handle. The door was locked, as he had anticipated. Kneeling down, he peered into the keyhole, holding the electric torch close beside his face and chewing industriously.
 
Ere long he stood up, descended again, but by the back stair, and stood staring reflectively at the door communicating with Ka............