The Sign of the Four is the second novel by British Writer Sir Arthur Conan Doyle featuring Sherlock Holmes.The story begins on a foggy day in 1888 when Dr. Watson confronts Holmes about his cocaine use. Holmes is bored because he has no problem to solve; shortly thereafter Miss Mary Morstan arrives with a case.Miss Morstan tells Holmes that her father Captain Arthur Morstan has arrived in London on a leave from the Andaman Islands.He requested her to be in Langham Hotel, but he is missing when she arrived.She contacted Major John Sholto who worked with her father, but he denied having seen Morstan.Holmes, Watson, and Mary meet with Sholto's son Thaddeus, the anonymous sender of the pearls, who explains that Morstan had visited Major Sholto to demand his half of a great treasure.Where is Arthur Morstan, is he alive or dead? How will Holmes solve the case? Read the book to know how Holmes solves the mystery.