In 2003, Dr. Serena Kogan (Helena Bonham Carter) of Cyberdyne Systems convinces death row inmate Marcus Wright (Sam Worthington) to sign over his body for medical research following his execution. One year later, the automated Skynet system is activated, becomes self-aware, begins to perceive humans as a threat, and eradicates much of humanity with nuclear weapons in the event known as "Judgment Day".
In 2018, John Connor (Christian Bale) leads an attack on a Skynet base, where he discovers human prisoners and schematics for a new type of Terminator, incorporating living tissue (The T-800). He is the only survivor of the assault after the base is destroyed in a nuclear explosion. Following Connor's departure, Marcus emerges from the base's wreckage and begins walking towards Los Angeles, after taking the clothing from a Resistance soldier, who died in the explosion.