In 2029, Earth has been ravaged by the war between the malevolent artificial intelligence Skynet and the human resistance. Skynet sends the T-1000—an advanced, shape-shifting prototype Terminator made of virtually indestructible liquid metal—back in time to kill resistance leader John Connor when he is a child. To protect Connor, the resistance sends back a reprogrammed T-800 Terminator, a less advanced metal endoskeleton covered in living tissue.

In 1995 Los Angeles, John’s mother Sarah is incarcerated in Pescadero State Hospital for her violent efforts to prevent “Judgment Day”—the prophesied events of August 29, 1997, when Skynet will gain sentience and, in response to its creators’ attempts to deactivate it, incite a nuclear holocaust. John, living with foster parents, also considers Sarah delusional and resents her efforts to prepare him for his future role. The T-1000 locates John in a shopping mall, but the T-800 intervenes, coming to John’s aid and enabling his escape. John calls to warn his foster parents, but the T-800 deduces that the T-1000 has already killed them. Realizing the T-800 is programmed to obey him, John forbids it to kill people and orders it to save Sarah from the T-1000.

The T-800 and John intercept Sarah as she is making an escape attempt, but Sarah flees in horror because the T-800 looks identical to the Terminator sent to kill her in 1984.[b] John and the T-800 persuade her to join them, and they escape the pursuing T-1000. Although distrustful of the T-800, Sarah uses its knowledge of the future to learn that a revolutionary microprocessor, being developed by Cyberdyne engineer Miles Dyson, will be crucial to Skynet’s creation. Over the course of their journey, Sarah sees the T-800 serving as a friend and father figure to John, who teaches it catchphrases and hand signs while encouraging it to become more human-like.