John finds himself battling an unlikely opponent alone; Derek and Charley search for the family after an explosion; and Ellison deals with the aftermath of Cromartie's massacre.
Sarah, Derek and Cameron try to prevent a nuclear meltdown, Charley has to fill in Michelle when James shows up at their home, and John meets someone new.
Cromartie uses Charley and Michelle in a plot to lure Sarah into the desert and leave John alone and vulnerable in the city. Meanwhile, Catherine Weaver has a job proposal for Agent Ellison.
Another malfunction causes Cameron to believe that she is actually a human from the future named Allison. Sarah accompanies her pregnant landlady to the hospital. Ellison continues to contemplate Catherine Weaver's job offer.
John and Derek sign on for military school to protect a key future Resistance hero from termination. Back at home, Sarah and Cameron protect a young boy who shares the same name as the intended target.
While Sarah and Cameron search for the person who robbed the house, Cromartie returns to hunt down Cameron and John. Meanwhile, a new cyborg arrives and creates trouble for Ellison.
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 turns to Dr. Sherman when she begins having nightmares, Jesse tries to convince Derek that she has captured an important figure from the future, and John and Cameron discover that Cromartie's body is missing.
Sarah's quest to find the meaning behind the "three dots" leads to a technology firm seeking an advanced microchip. Dr. Sherman is killed while working with Catherine Weaver's A.I. computer, and Jesse comes clean about her mission.
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."
Sarah has visions of John's dead father as she tries to find a doctor to remove a bullet from her leg, Jesse removes Riley from the hospital after her suicide attempt, and Catherine covers her tracks after a secret location is identified.
Sarah attends a memorial service for Catherine Weaver's victims at the supposed heating and air conditioning plant to search for answers and find a connection to Skynet.
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.
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 recalls more of her fateful future mission aboard the Jimmy Carter. Back in the present, her plan to turn John against Cameron backfires when John discovers that Jesse - not Cameron - killed Riley.
Sarah and John hit the road without Cameron and Derek to stay with Charley Dixon, where she reveals to Charey that her cancer may have emerged. Meanwhile, a computer worm infects John Henry.
Sarah, John and Cameron save Catherine Weaver's daughter Savannah from being killed by a machine, but Derek is killed in the process. Ellison is then forced to broker a meeting between Sarah and Catherine to return the child.
Sarah is in police custody, but John and Cameron disobey her orders and help her escape. The three then go to Zeira Corp so that Sarah can confront Catherine Weaver, and Cameron can confront John Henry.
