The Dark Half
by Stephen King
Thad Beaumont is an author and recovering alcoholic who lives in the town of Ludlow, Maine. Thad's own books – cerebral literary fiction – are not very successful. However, under the pen name "George Stark", he writes highly successful crime novels about a violent killer named Alexis Machine. When Thad's authorship of Stark's novels becomes public knowledge, Thad and his wife, Elizabeth, decide to stage a mock burial for his alter ego at the local cemetery, which is featured in a People magazine article. Stark's epitaph says it all: "Not A Very Nice Guy." Stark, however, emerges from the mock grave as a physical entity, complete with the personality traits that Thad exhibited while writing as Stark, such as drinking heavily and smoking Pall Mall cigarettes. He then goes on a killing spree, gruesomely murdering everyone he perceives as responsible for his "death" – Thad's editor, agent, and the People interviewer, among others. Thad, meanwhile, is plagued by surreal nightmares. Stark's murders are investigated by Alan Pangborn, the sheriff of the neighboring town of Castle Rock, who finds Thad's voice and fingerprints at the crime scenes. This evidence, and Thad's unwillingness to answer his questions, causes Pangborn to believe that Thad – despite having alibis – is responsible for the murders. Later, it's discovered that Stark has the same fingerprints as Thad, a clue to the twinship he and Thad share.
Thad eventually discovers that both he and Stark share a mental bond, and begins to find notes from Stark written in his own handwriting. The notes tell Thad what activity Stark has been engaging in. Observing his son and daughter, Thad notes that twins share a unique bond. They can feel each other's pain and at times appear to read the other's mind. Using this as a key to his own situation, he begins to discover the even deeper meaning behind himself and Stark.
Pangborn eventually learns that Thad had an unborn twin brother who was absorbed into Thad in utero and later removed from his brain when the author was a child. He had suffered from severe headaches and it was originally thought to be a tumor causing them. The neurosurgeon who removed it found the following inside: part of a nostril, some fingernails, some teeth, and a malformed human eye. This leads to questions about the true nature of Stark, whether he is a malevolent spirit with its own existence, or Thad himself, manifesting an alternate personality. Thad eventually destroys Stark, but the book ends on an unhappy note with Thad's wife having serious doubts about the future of their relationship: she is appalled that Thad not only created Stark (if unintentionally), but that a part of him liked Stark.