The pencil paused. Then it wrote words that answered the question:
Because certain persons must know that Berger murdered Graham. Those persons do not want the crime to be discovered. Those persons must be connected with the crime.
Another pause — a longer pause. Then:
Berger was directed by some one. He possesses no written evidence. He received instructions verbally. Where?
The pencil hesitated a few seconds only. Then it inscribed these statements:
Instructions were given at some unknown meeting place. Berger was summoned to that place. Probably more than once. The blank cards have special meanings.
The long, slender hand thrust the pencil out of sight in the folds of a dark coat. It reappeared, carrying a fountain pen. It wrote upon a black card, in red ink:
Come for instructions to-night.
The hand stacked the three black cards. The writing explained their meaning.
Stanley Berger had received them at different times. Each card was a summons to attend a meeting.