The plot concerns a super-intelligent AI system called Skynet which has taken over the world by initiating nuclear war. Amid the resulting devastation, human survivors stage a successful fightback under the leadership of the charismatic John Connor.
In response, Skynet sends a cyborg assassin (played by Arnold Schwarzenegger) back in time to 1984 – before Connor's birth – to kill his future mother, Sarah. Such is John Connor's importance to the war that Skynet banks on erasing him from history to preserve its existence.