Sarah Connor runs into a school and finds her son, John in the library. Police wait outside. A man walking to the scene reveals machine guns and begins to fire. John escapes and runs. Sarah grabs a pistol and fires at the man, but the bullets bounce off the man's head. The man aims and shoots John in the back. Sarah huddles over John's dead body. A massive explosion erupts behind them. The man's skin peels away to reveal a robot endoskeleton. He's a terminator.
Sarah snaps awake. It was a dream. It wakes up her fiance, Charlie. Charlie heads off to work. Sarah wakes John up, tells him it's not safe and he needs to pack. They're leaving town.
Charlie reports Sarah gone at a local police station. Charlie meets Agent James Ellison, who reveals Sarah's true identity and her past.
As Sarah and John flee, Ellison updates a database. At an abandoned warehouse, Sarah's profile appears. A man in the back stands and reads the screen.
John starts his first day at a new school. Cameron, a pretty girl, introduces herself to John.
A substitute teacher takes roll. The teacher, Cromartie, is a Terminator. John answers. Cromartie pulls a gun from his leg. He fires, and Cameron takes the bullets in the chest. John escapes out the window. Cromarite chases John into the parking lot. Cromartie tracks John, and is about to make his kill. A pick-up truck plows him down. Cameron, behind the wheel, kicks open the door. John jumps in. John realizes Cameron is a Terminator also.
Sarah hears the news and races to the school. Sarah watches the school from a distance. Cromartie grabs her and calls John, mimicking Sarah's voice. John says he is returning to the house.
At the house, John walks in. Cromartie fires his gun. When he goes to see the body, it's Cameron. She springs up and battles Cromartie. The two demolish the house. Cameron uses an electrical line to short circuit Cromarite and the three escape.
While John sleeps, Sarah asks Cameron about the future. Someone else builds Skynet. Cameron is there to protect John.
Sarah, John and Cameron start with the widow of Miles Dyson, Theresa. Outside, Cromartie closes in. Sarah races out of the garage, backing over Cromartie. Cromartie returns machine gun fire. They escape, but Sarah was hit by gunfire.
The next morning Cameron leads them into a bank. Cameron draws a gun, a teller sounds the alarm. Another teller takes them to the safety deposit vault, and locks them in. Cameron has John and Sarah open several boxes, all with odd pieces in them. Cameron assembles the pieces into a large gun.
Cromartie arrives and begins to tear the vault door down. Cameron scrambles and reveals a secret time machine. Cameron activates the machine, Sarah holds the gun towards the door. Cameron activates the time machine, and Sarah fires as Cromartie enters.
The three arrive naked on a busy freeway 8 years in the future. After retrieving some clothes, the three set out to stop Skynet.