"Open it," said the colonel in a low voice; "open it, Crewe"--he pulled open the drawer and took out something--"and if it is Jack o' Judgment----"

Crewe opened the door, his heart beating at a furious rate, but it was Selby who came into the room and faced the half-levelled gun of the colonel.

"What do you want?" asked Boundary quickly. "You fool, I told you not to lose sight of her----"

"But when is she coming down?" asked Selby. "I've been waiting there all this time and there's a policeman at the corner of the street--I wondered whether you had seen him too."

"Not come down?" said the colonel. "She left here five minutes ago!"

"She hasn't come down," he said, "and I've certainly not passed her on the stairs. Is there any other way out?"

"No way that she could use," said the colonel shaking his head. "I've had new locks put on all the doors." He thought a moment. "If she hasn't come down she's gone up."

They went up the stairs together and searched, first Pinto's flat, and then the store-rooms and empty apartments on the floor higher up.

"Go down to the door and wait, in case she tries to get out," said the colonel.

He returned to the room with the two men and they looked at one another in frank astonishment.

"Have you any idea what's happened, Crewe?" asked the colonel suspiciously.

"No idea in the world," said Crewe.

"But she went downstairs," said the colonel. "I heard the alarm click."

"The alarm?" questioned Crewe.

"I've got a buzzer under one of the treads of the stairs," said the colonel. "It is useful to know when people are coming up."

* * * * *

Ten minutes passed and Selby returned to say that the policeman had been making inquiries as to whom the car belonged.

"You'd better get it away," said the colonel, "and send away your men."

"They've gone," said the other. "I wasn't taking any risks."

He disappeared to carry out the colonel's instructions, and they heard the whine of the moving car.

Boundary unlocked his tantalus and took out a full decanter of whisky. Without a word he poured three stiff doses into as many glasses and filled them with soda. Each man was thinking, and thinking after his own interests.

"Well, gentlemen," said the colonel at last. "I incline to give this business best."

He looked up and saw the dagger which Pinto had thrown. It was still embedded in the wall.

"It isn't enough that I should have Jack o' Judgment messing my room about," he growled, "but you must do something to the same wall! Pull it out and don't let me see it again, Pinto."

The Portuguese smiled sheepishly, walked to the wall and gripped the handle. Evidently the point had embedded in a lath, for the knife did not move. He pulled again, exerting all his strength and this time succeeded in extracting not only the knife but a large portion of the plaster and a strip of the wallpaper.

"You fool!" said the colonel angrily, "see what you have done--Jumping Moses!"

He walked to the wall and stared, for the dislodgment of plaster and paper had revealed three round black discs, set flush with the plaster and only separated from the room by the wallpaper, which had been stripped.

"Jumping Moses!" said the colonel softly. "Detectaphones!"

He took Pinto's knife from his hand and prised one of the discs loose. It was attached to a wire which was embedded in the plaster and this the colonel severed with a stroke of the knife.

"This is the business end of a ............