The book follows two related but separate narrative threads: episodes from Oswald's life from his childhood until the assassination and his death, and the actions of other participants in the conspiracy. A secondary parallel story follows Nicholas Branch, a CIA archivist of more recent times assigned the monumental task of piecing together the disparate fragments of Kennedy's death.
Oswald is portrayed as a misfit antihero, whose overtly communist political views cause him difficulties fitting into American society. Raised by a single mother in The Bronx, Oswald enlists in the military in the 1950s and is stationed at the Naval Air Facility Atsugi in Japan, where he amuses his fellow marines with his earnest left-wing ideology. Oswald defects to the Soviet Union after the end of his service and is interviewed by the KGB about the U-2 reconnaissance planes he observed at Atsugi, although he is unable to furnish much useful information. Following a suicide attempt, Oswald is moved to Minsk, where he works in a factory and meets a young woman, Marina, whom he marries. In the early 1960s, Oswald and Marina relocate to Texas.
Concurrently in the novel, a cadre of CIA agents disillusioned by Kennedy's perceived failure to adequately support the Bay of Pigs invasion hatch a plot to stage an assassination attempt and blame it on the Cuban government. The chief conspirators in the CIA are Win Everett, Lawrence Parmenter and TJ Mackey. The conspiracy grows to encompass several largely independent factions, including organized crime figures in New Orleans and a contingent of Cuban exiles in Miami. Although at first they planned to intentionally miss the President, at some point it is decided that the gunman should aim to kill.
After Oswald's return from the Soviet Union, he comes to the attention of the conspirators, who realize that his history of public support for communism makes him a perfect scapegoat. They make contact with him and guide him along the path to the assassination. Oswald also meets a fellow serviceman in Dallas who has become a black nationalist, and the two men attempt an assassination of the far-right General Edwin Walker in his living room.
On November 22, 1963, as President Kennedy's motorcade is passing through Dealey Plaza in downtown Dallas, Oswald shoots at him from the Texas School Book Depository, while a small group of Cuban exiles fires from behind the grassy knoll. Oswald is able to escape the scene of the crime because, as an employee of the Depository, the police do not identify him as a suspect. Later that afternoon, he shoots a Dallas patrolman who stops him for suspicious behavior. Oswald goes to a movie theater where the CIA conspiracy had planned to have him killed, but before they can do so he is apprehended by the Dallas police. A few days later, Oswald is murdered in police custody by Jack Ruby, a nightclub owner with underworld connections who was manipulated into killing Oswald by the conspirators.
At the end of the novel, Oswald is buried under an alias in a grave in Fort Worth in a small ceremony attended by his immediate family members.
