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 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.

Sarah and Cameron investigate a nuclear power plant; John grows less enthusiastic about academics but flourishes socially with the help of a new friend; Catherine Weaver gets another piece of the puzzle for her pet project.

Derek and Sarah must outwit Cromartie after he kidnaps Charley's wife, and they must weigh the consequences in rescuing her. Meanwhile, John finds himself unable to choose between Cameron and Riley.