“Then, with death staring at him, he turned to another scheme more insidious than idle threats or inferences.
“He arranged the killings — and sent the death notes!”
“But how?” came Cardona’s question.
“One came from this floor tonight,” said Biscayne thoughtfully. “There was no one here to mail it.
“Look at the side wall of this room. The mail chute must be on the other side—”
Cardona was tapping at the wall. Eagerly he searched, and the others joined with him. Keen though these men were, the secret mocked them.
“We’ll smash that mail chute!” exclaimed Cardona grimly. “Wait until I get Mayhew. We’ll find it from the other side—”
“Here!” The cry came from Biscayne. He was rapping at the baseboard of the wall. “This may be it!”
Cardona was with the professor. Together, they pried effectively. The small portion of flooring yielded. The baseboard came open.
The little cache was disclosed. The clockwork was still ticking, but now there was no letter projecting from the clips.