“Look here,” he said, glancing out of the corner of his eye to be sure that Laura was there, “let me show you what I have just discovered.”
He felt with his thumb for a spring. In a moment or two a portion of the wall, about two feet in extent, slowly revolved, disclosing a small cupboard fitted with a telephone instrument.
“A telephone,” the Inspector remarked, pointing to it, “in an unoccupied house and a concealed cupboard. What do you think of that?”
The Professor shook his head.
“Don’t ask me,” he groaned.
French took the receiver from its rest and called up the exchange.
“Inspector French speaking,” he announced. “Kindly tell me what is the number of the telephone from which I am speaking, and who is the subscriber?”
He listened to the reply and asked another question.
“Can you tell me when this instrument was last used?… When?… Thank you!”
The Inspector hung up the receiver.