"In Cold Blood" is summarized as two parallel storylines. The first storyline is set in Kansas, where members of the Clutter family are murdered. It follows the police investigation led by Alvin Dewey. The second storyline follows the murderers, Perry Smith and Dick Hickock, as they attempt to outrun arrest.
The summary reveals that "In Cold Blood" spans multiple years: From the initial murders of the Clutter family and the police investigation, to a five-year appeal process, to the eventual deaths of the murderers on death row. In this time, new characters come in and out of the story such as Floyd Wells, a prisoner who provides the police with new leads. The focus of the summary, however, is on the two murderers, Perry and Dick.
Additional information is provided about Perry's childhood and his lack of family support and structure. In the end, this creates more sympathy for his character when he is described as remorseful prior to his execution. Dick and Perry's efforts to evade arrest are successful until they run out of money. They hide in Mexico, the American desert and Miami. They are eventually caught when a police officer in Las Vegas recognizes their license plate.