- "I'm a killer. You know I'm a killer. But did you know I'm a cereal killer?"
- ―Smith, advertising cereals.
Culverton Smith is a prominent entrepreneur and philanthropist, using his fame and fortune to help many charities. However Smith is secretly a serial killer, likely killing hundreds of people, who doesn't kill out of hate or love, but for the pleasure of killing. Using his wealth and unassailable power, he is able to use his charity-funded hospital as a way to go into patient's rooms and then kill them, taking inspiration from H. H. Holmes. Smith also has an uncontrollable need to confess to his crimes, going as far as to confess to his closest friends, even his daughter Faith, but making them forget his crimes by inducing them to a memory inhibiting drug. Sherlock comes up against Smith when Faith gives him a slip of paper that she wrote down, reminding her of fragments of the crimes Smith told her. Sherlock comes to suspect Smith of being a serial killer, garnering media attention, which forces Sherlock and John to go with Smith to his hospital. After Sherlock tries to attack Smith with a scalpel, he is taken in as a patient to recuperate from drugs. Smith attempts to kill Sherlock, believing him to be a threat. Sherlock manages to make Smith confess, his confession is recorded via a device hidden in John's cane, and thus is arrested. After being interrogated by Lestrade, Smith finds that confessing was more enjoyable than he imagined, and "should have done it sooner". He also realizes that this confession will make him even more famous, and that he may be able to "break America".
Culverton Smith is nothing more than the ultimate personification of psychopathy, sadism, and narcissism. Culverton is described as being "the worst person in London", Sherlock's darkest foe yet. Culverton doesn't murder people out of hate or love, but simply because he enjoys killing, and turning people into "things". This makes him vastly different from past foes like Jim Moriarty, who was psychopathic, but also charming and had ulterior motives, and Magnussen, who was blank and amoral, yet had a reasoning behind his behaviour. Culverton simply kills his victims out of amusement.
Culverton is a sadistic and psychopathic serial killer who cares for no one. He has an uncontrollable need to confess his crimes, and is often not taken seriously when he does so, mainly due to the amount of power he holds. Culverton comes off as charming, but when people question him, he can quickly shift to a more horrifying personality, going as far to threaten those who annoy him.
Culverton is also narcissistic, arrogant, and overconfident, believing that he could outsmart, and even kill Sherlock. He is also an incredible liar, as he was able to fool everyone, except Sherlock.
Culverton is the most prolific undetected serial killer in the history of Britain, his kill count likely in the high hundreds, possibly over three hundred. Culverton is remorseless, and emotionless towards his victims. He also enjoys the actual moment of death, seeing his victims take their last breath.
Sherlock is actually appalled by Culverton, and stated that he was the most evil, and despicable man he had ever come across, a human coagulation of evil. Culverton rivals Magnussen's ability to disgust Sherlock.
- He is based off Culverton Smith from The Adventure of the Dying Detective.
- In the episode "The Six Thatchers", his photo can be seen on a bus stop advertisement.
- Smith is a big fan of H.H.Holmes and recreates his Murder Castle by using his hospital wing; he kept firing architects and replacing them, so only he knew how everything fitted together, allowing him to use secret passages to sneak around and kill without any witnesses.
- Smith is largely based on Jimmy Savile. Savile was a highly eccentric TV and radio personality who was famed for raising massive amounts of money for charity. After his death in 2011 it was revealed that he had sexually abused hundreds of children, adults and patients. He used his celebrity status to access hospitals, childrens wards and even morgues. He also tended to admit to certain aspects of his crimes, but was often dismissed as jokes as part of his persona.