The blow had not been a hard one, yet it had momentarily stunned Doctor Palermo’s servant. Before Hassan could recover, the man in the black cloak had sprung from the elevator, carrying the black bag.
As Hassan groaned and opened his eyes, the man pulled a rag from the bag and held it to the Arab’s nose. The odor of chloroform pervaded the anteroom. Hassan lay still.
“Going down,” said Burbank, the elevator operator. His voice was methodical. His face was calm and expressionless. “Will fake a call when Palermo returns. Telephone bell will warn you,” he added in a guarded tone.
The door of the elevator closed while the man in black was still nodding his approval.
FROM the bag, the mysterious visitor removed two straps. He dragged Hassan’s body into the apartment and closed the door behind him. He used the straps to bind the Arab.
He left the bag at the door and began to walk about the apartment. The place seemed unfamiliar to him.
Cautiously he tried the door to the laboratory. It was locked. He could not find the key on Hassan.
He abandoned the search and walked through the apartment. He came to the panel that concealed the secret stairway.
Here he made no pretext at the theatrical finger-snapping performed by Doctor Palermo for the mystification of his visitors. He simply sought the floor plates beneath the rug. When he stepped on them properly, the door slid open.
The man in black went up the stairs. There was something cumbersome about his movements. He was proceeding cautiously.