Fumbling with the mechanical box, Cardona pried off the lid.
The interior of the box showed a set of thin sections, more than twelve in number, each slightly larger than an envelope.
“One every forty-eight hours,” said the detective to Biscayne. “That’s how it was set—”
“No,” said Biscayne, “it must have been gauged for twenty-four. That’s why the Sutton letter came in between the death notes.
“By leaving empty spaces, the deliveries could be interrupted on days they were not needed.”
“Right,” declared Cardona.
Biscayne began to pace up and down the room. His mind was at work.
“If I had known Harshaw well,” said the professor, “I might have divined some of this beforehand.
“Three men have died because of his fiendish plotting. We can be thankful only that the fourth was saved — my cousin, Arthur Wilhelm.
“Silas Harshaw was unquestionably eccentric,” Biscayne continued. “He imagined enmities, and saw schemes where there were none.