The second Holmes novel, commissioned directly by the editor of Lippincott's Monthly Magazine at a dinner that also produced Oscar Wilde's The Picture of Dorian Gray. The investigation centres on a stolen treasure, a wronged woman, and a chase along the Thames, and introduces Mary Morstan. The Sign of the Four deepens Holmes's characterisation considerably, including his cocaine use and his philosophical outlook, while delivering a more conventionally satisfying adventure plot than its predecessor.
