p 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,