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.

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.

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.

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.

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.

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.

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."

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.

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.

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.