As a practical joke, Sub-Inspector Dick Martin, about to retire, is asked to find a stolen library book. Before long, Dick finds himself intrigued by the nature of the book—and the attractiveness of Sybil, the librarian. Now in private practice, Dick accepts a job that requires him to chase an elusive nobleman, Lord Selford, across the world and is subsequently surprised to find that his favorite librarian is Selford’s relative. Events take a turn when a safe-cracking expert is murdered after attempting to break into the Selford family crypt, and Dick investigates. The Door with Seven Locks contains the locked-room puzzle for which Edgar Wallace was famous, but it’s also notable for its exploration of the concept of nature versus nurture. This book is part of the Standard Ebooks project, which produces free public domain ebooks.