In 2003, Dr. Serena Kogan of Cyberdyne Systems convinces death row inmate Marcus Wright to sign over his body for medical research following his execution. Some time later, the automated Skynet system is activated and becomes self-aware; perceiving humans as a threat to its existence, it starts a nuclear holocaust to eradicate them in the event known as "Judgment Day".
In 2018, John Connor leads an attack on a Skynet base, where he discovers human prisoners and schematics for incorporating living tissue to a new type of Terminator, the T-800. John survives an explosion on the base, which is destroyed. Following John's departure, Marcus emerges from the base's wreckage and begins walking towards Los Angeles.