Arthur Conan Doyle 
The Sign of the Four 

The Sign of the Four is the second of Arthur Conan Doyle’s Sherlock Holmes novels. The detective and his companion, Dr. Watson, unravel the mystery of hidden treasure and murder.
Miss Mary Morstan arrives at 221B, Baker Street and asks for help with the mystery of her disappeared father, an anonymous pearl gift, and a letter asking her to meet an unknown person that evening. Holmes takes the case and the adventure begins.