The Puzzle Lock

An elderly London dealer in jewels and antiques, a man full of cranks and oddities, walks out of a restaurant with a flashy acquaintance and is not seen again. His office holds a strong-room with no keyhole and no key: fifteen lettered discs, and some forty billion possible settings. Scotland Yard can neither open it nor prove that any crime has been committed.

What Dr. Thorndyke has to work with is smaller: a wax squeeze of a signet ring engraved with four lines of schoolboy Latin doggerel, and a caretaker's complaint that thirty watts of current are leaking somewhere inside the empty premises. Quiet, exact scientific detection, every fact the investigator holds laid in front of the reader.