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 Derek Reese 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.

Sarah finds herself in a business transaction with a mysterious business man named Sarkissian, who claims to be in possession of the stolen Turk computer system and wants an exorbitant amount of money for it. Derek recalls his childhood before the so-called Judgement Day in 2011, when a nuclear war triggered by Skynet will destroy the world. Agent Ellison finally discovers that the terminator Cromartie is impersonating an FBI agent, and makes arrangements to apprehend him.

After the Jeep explosion, John's 16th birthday makes him confront the fact that he's destined to be alone. Meanwhile, after Cromartie's massacre, Agent Ellison must face off against both the Feds and his faith.

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.

A software glitch causes Cameron to forget who she is. She goes missing from the Connors and is taken in by a street kid named Jody. Cameron and Jody end up at a halfway house where Cameron meets with a social worker who uncovers some of Cameron’s distant memories. Meanwhile, Catherine Weaver meets with Agent Ellison to discuss his future at Zeira Corp, and Ellison does some digging into Weaver’s past.

John and Derek infiltrate a military academy in order to protect an integral member of the future resistance. Meanwhile, Weaver’s first assignment for Ellison takes an interesting turn of events when he discovers a specter from his own past.

While Sarah, John and Cameron track another name from their list, they accidentally cross paths with T-1001. Meanwhile, a woman who Derek once knew in the past surprises him by appearing in the present.

The Connors find themselves on high alert and in odd company after their house is robbed. A Terminator terrorizes Ellison, while another gets dangerously close to John Connor. Derek and Jesse continue to get reacquainted.

Cromartie kidnaps Sarah and races to Mexico to find John. When Derek, Cameron and Ellison discover what has happened, they come to their defense, which leads to one final deadly confrontation with Cromartie.

Sarah finds that the strange dreams she's been having while she sleeps are slowly beginning to creep into her waking life, but she has no idea what the dreams mean for her and John. Derek and Jesse investigate a possible Skynet conspirator.

Sarah's quest to find the meaning behind the "three dots" leads to a technology firm seeking an advanced microchip. Meanwhile, Jesse comes clean to Derek about her mission and Weaver makes an important introduction.

Cameron learns that a terminator was accidentally sent back to 1920s Los Angeles, and she tries to find out what happened to him. Meanwhile, John has a run-in with a group of punks while taking Riley home from a party.

Terminators come after a family whose unborn daughter plays an important role in the war against the Machines, and Sarah, Cameron, and Derek try to protect them.

Sarah turns to a UFO convention for answers about the "three dots," more details about Riley's mission are revealed, and Ellison begins working with Catherine Weaver's AI prototype, "John Henry."

While fighting to stay alive, Sarah is guided by the image of John's father. Weaver's attempt to protect John Henry has deadly consequences.

The Connors visit a town connected to the destroyed factory; Weaver sends a man into town in search of a survivor.

Sarah suspects that something fishy is going on at the medical clinic where she is being treated for insomnia. During her stay, she has flashbacks to a run-in she had with a man from the plant whom she thought she had already killed.

While Derek does surveillance on a lawyer he suspects may be connected to Skynet, Sarah and Cameron begin to have doubts about Riley.

As the Connors prepare to move, they find out that Riley is dead, and Sarah begins to doubt Cameron's motives. Jesse flashes back to a submarine mission in the future, and John Henry plays hide and seek with Catherine Weaver's daughter.

Jesse's submarine mission in the future takes a fatal turn with unforeseen consequences. Back in the present, her plan to turn John against Cameron backfires when John discovers that Jesse--not Cameron--killed Riley and he makes a life-or-death decision.

Sarah and John hit the road without Cameron and Derek to stay with Charley Dixon, where she reveals to Charley that her cancer may have emerged. Meanwhile, a computer worm infects John Henry.

When John attempts to rescue Skynet’s latest target he finds himself closing in on Weaver, but at what cost? Game plans change, causing Sarah and Ellison to reunite. Meanwhile, Weaver learns Ellison’s secrets.

Fate is changed forever on the explosive season finale episode! The Connors come face-to-face with Weaver in a confrontation that shakes John to the core and changes his reality. Nothing will be the same.