The hand stopped writing. It began to tap the pencil against the paper, counting the seconds that were marked by a watch that lay on the table.
The brain in the darkness was going through the murder of Jonathan Graham, counting from the very instant when Berger pushed the millionaire through the window until the moment when the secretary screamed his warning.
Thirty taps. Then the hand wrote:
Half a minute at the most. No one knows the exact minute at which Jonathan Graham’s body crashed to the street. The time element is perfectly in Berger’s favor. Berger’s alibi is now perfect — to the unthinking minds of those who were in the office — and to the minds of the police. But to the deductive brain, Berger’s action betrays his crime.
The right hand picked up the paper, and crumpled it into a ball. The hand disappeared and returned without the paper. Then on another sheet, it wrote:
Stanley Berger murdered Jonathan Graham.
The pencil remained still for two short seconds; then it moved again, and the hand inscribed these words:
The Shadow knows!