Culverton Smith was a British planter, resident in Sumatra in the Dutch East Indies. He was also an amateur bacteriologist, and maintained a collection of virulent disease cultures. He used this collection to murder his nephew Victor Savage for an inheritance, and later attempted to murder Sherlock Holmes the same way during his investigation in "The Adventure of the Dying Detective".
Holmes was suspicious of of Savage's death: he had taken ill and died suddenly of a rare tropical illness in London. When Smith learned that Holmes was investigating, he attempted to kill him the same way he had killed his nephew: a trick box with a sharp spring poisoned with a deadly infection. Holmes, fortunately, perceived the trap, and decided to pretended to take ill, believing that Smith would likely confess to him if he believed his plan had worked.
Holmes tricked John Watson into believing that he was dying, and asked him to bring Smith to him, telling Watson Smith was the one man with the knowledge to cure him. When Smith heard that Holmes was seriously ill, he gleefully went to Baker Street. Not knowing that Watson was concealed in the room, he gloated about the success of his plans to kill Savage and Holmes. Holmes then reveals that he faked the illness, and Inspector Morton enters to arrest Smith. Though Smith asserts his supposed confession is worthless in court, with Holmes' word against his own, Watson emerges and corroborates Holmes' story, and Smith is taken to prison.
Smith was arrogant, vindictive, and cruel, and believed himself unmatched in intelligence. Watson describes Smith as having "a great yellow face, coarse-grained and greasy, with heavy, double-chin, and two sullen, menacing gray eyes which glared at me from under tufted and sandy brows. A high bald head... The skull was of enormous capacity, and yet... the figure of the man was small and frail, twisted in the shoulders and back like one who has suffered from rickets in his childhood."
- In the Granada adaptation of "The Dying Detective", he is portrayed by Jonathan Hyde. The episode expands significantly on Smith's relationship with Victor Savage, who is portrayed as his cousin.
- Culverton Smith appears as the main villain of the Sherlock episode "The Lying Detective", portrayed by Toby Jones. However, portrayal is significantly different from the original story.