The series picks up four years after the events of Terminator 2: Judgment Day with John and Sarah Connor hiding from the government. After two years in one place Sarah decides they need a change of scenery. Cameron Phillips, a reprogrammed Terminator sent to protect John, informs them that Judgment Day was not stopped and will take place in 2011.
After two years in one spot Sarah Connor feels the need to move on before they get too comfortable. They move to a new city where John starts school and meets a mysterious girl. However, danger strikes, and Sarah and John are caught in another struggle for their survival.
Sarah makes contact with an old friend to ask a favor, while John decides to pay a visit to Sarah's ex and Cameron makes a new friend. Together they infiltrate a resistance safe house and discover they are not alone. Meanwhile, Agent Ellison realizes that Sarah is still alive and a dangerous person from Sarah's past is reawakened.
Sarah visits Miles Dyson's widow to find the creator of Skynet. She leads her to a man named Andy Goode who used to work with Dyson and is building a chess-playing computer named "The Turk." John and Cameron try their best to fit in on their first day at a new high school.
While searching for some stolen cargo, John becomes separated from Sarah and Cameron. Meanwhile, Agent Ellison's murder investigation leads him to a surprising suspect.
Sarah reevaluates the capabilities of her friend Andy's computer after he enters it in a chess competition. During the competition Sarah meets a stranger with a history similar to hers. Meanwhile, Agent Ellison finds remnants from a past terminator battle.
Flashing in and out of consciousness, fighting for his life, the Stranger from last week recalls his future life battling the machines in 2027. Meanwhile, Sarah tries to explain the past to Charley.
Sarah breaks into Agent Ellison's apartment and discovers a file on her from her time at the mental hospital, leading her to Dr. Silberman, now a doomsday convert. Meanwhile Cameron signs up for a ballet class and John finds out how his mom escaped the mental hospital.
Derek finds the brain chip from Vick that Cameron had kept. John builds an interface for it and they discover a computerized traffic system is important to Skynet. Sarah decides it must be sabotaged. Meanwhile, Cromartie is checking through school records in search of John.
John defends Cameron against a damning accusation by Derek, putting him and Derek at odds, while Sarah finds herself in a business transaction with a mysterious business man. Meanwhile, Cromartie closes in on John and Agent Ellison discovers a nemesis at the agency. Part two of Season 1 Finale.