Stephen King wrote several stories under a pseudonymn, Richard Bachman, during the seventies. Most of the Backman novels were darker and more cynical in nature, featuring a far more psychological sense of horror than visceral. When King was discovered to be Bachman, he wrote The Dark Half in response to his outing.
King decided to use the idea of a writer having an alter ego to write novels. Thad Beaumont lives in the tiny Maine town of Ludlow (the setting of Pet Sematary and about an hour away from the fictional town of Castle Rock, often used in King's novels). His alter ego is George Stark, who writes gritty crime novels about a violent killer named Alexis Machine, which are very popular and successful. When it's learned that Thad Beaumont, who writes cerebral literary fiction, is really Stark, he and his wife Elizabeth decide to stage a daylight funeral for Stark. His epitaph at the local cemetery says it all: NOT A VERY NICE GUY.
However, that is not the end of Stark and over the weeks to come he resurrects himself from his mock-grave and kills, gruesomely, everyone he perceives responsible for his "death". Thad, meanwhile, is plagued by surreal nightmares and is soon visited by Alan Pangborn (a Sheriff later seen in the novel Needful Things), asking questions Thad can't answer, nor does he want to.
Thad experiences blackouts and comes to discover that he and Stark share a mental bond. He 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 others pain and at times appear to read the others mind. Using this as a keystone to his own situation, he begins to discover the even deeper meaning behind himself and Stark.
Pangborn eventually learns that Thad had a twin. The unborn brother was absorbed into Tad in utero and later removed from his skull when the author was a child. He had suffered from severe headaches and it was originally thought to be a tumor causing them. This leads to questions about the true nature of Stark, whether he's a malevolent spirit or Thad manifesting a multiple personality.
