Edgar Wallace 
The Door with Seven Locks [EPUB ebook] 

A short but interesting detective story. Dick Martin plans for an early retirement from the police force seeking a quite life. His final job is to bring in Lew Pheeney, wanted in connection with a bank robbery. When Lew confesses to trying to open a dead man’s tomb, however, Martin has a mystery he must unravel. He races to find the connection between an attractive young librarian, a mad scientist and the vanished heir to a vast fortune, as everyone becomes entangled in a web of fraud, deceit, torture and murder. What dangers did he face in understanding the mystery behind the door with seven locks? Combines a mystery thriller plot with considerable dashes of gothic horror, and just the faintest hint of science fiction.