John Connor has been living off the grid in Los Angeles following the death of his mother, Sarah. Although Judgment Day did not occur on August 29, 1997, John still fears a war between humans and the machines. Unable to locate John in the past, Skynet sends a new model of the Terminator called the T-X to July 23, 2003, to kill other members of the Human Resistance. The T-X is more advanced than previous Terminators, and has an endoskeleton with built-in weaponry, a liquid metal exterior similar to the T-1000, and can reprogram other machines. Unlike previous Terminators, its standard appearance is afemale. The Resistance sends a reprogrammed Terminator (T-850 – Model 101) to protect the T-X’s targets including John and his future wife, Kate Brewster.
After killing several other targets, the T-X locates Kate and John at an animal hospital, where the former works and the latter was stealing from; but they escape with the Terminator’s help. The Terminator takes John and Kate to a mausoleum where John’s mother is supposedly interred. Inside her vault, they find a weapons cache left at Sarah’s request in case Judgment Day occurred. Police arrive and a gun battle ensues, but the three escape in a hearse. The T-X also arrives and chases the Terminator and the others, but they escape. The Terminator reveals his plan to drive John and Kate to Mexico to escape the fallout when Judgment Day begins at 6:18 p.m. that day. John orders the Terminator to take him and Kate to see Kate’s father, a Lt. General who is supervising the building of Skynet after Cyberdyne Systems went defunct, and threatens to kill himself if the Terminator refuses. The Terminator calls John’s bluff but agrees to take them after Kate orders him to. The Terminator reveals that he killed John on July 4, 2032; Kate sent him back from the future after having him captured and reprogrammed.
At the Air Force base, General Brewster faces pressure from the President to activate Skynet to stop a computer virus infecting computers all over the world, unaware that the virus is Skynet establishing control over the worldwide computer network. John and Kate arrive too late to stop Skynet from being activated, and its machines begin attacking the staff. Brewster is mortally wounded by the T-X, which arrived before John, Kate, and the Terminator. Before dying, he gives Kate and John a code book and the location of what John believes is Skynet’s system core. John and Kate head for the tarmac to take General Brewster’s airplane to reach Crystal Peak, a military base built inside the Sierra Nevada that is hardened against nuclear attack. The T-X and the T-850 battle, and the T-X severely damages the T-850 before reprogramming it to kill John and Kate. The T-X pursues John and Kate through the military base but becomes trapped when a particle accelerator is activated and the magnetic field bonds it to the accelerator. In the hangar, the Terminator, unable to control his outer functions but still consciously aware, attacks John and Kate before John convinces it to reject the T-X’s control, and deliberately shuts its corrupted system down, enabling John and Kate to escape. Shortly after they leave, the Terminator’s system reboots.