A time displacement sphere appears and a seriously injured man staggers out of it. Sarah, Derek and Cameron are preparing to move into a new home when the man crashes in. He reveals himself as a resistance agent and gives information on a man named Greenway and the Serrano Point Nuclear Power Plant before he dies.
The trio head to the plant, triggering a memory for Derek. He recalls that the Resistance recaptured the plant from Skynet in the future. The girls get hired at the plant as janitorial engineers as the plant is being set up for reactivation, to find out why it is so important.
Sarah gets close to nuclear technician and scarred cancer survivor Greenway, who doesn't want to reactivate the plant. His co-workers, however, dislike him intensely and think that he is being over cautious.
Sarah is faced with a dilemma. If the plant is activated as an unsafe facility, Skynet reaps the benefits of the huge human death toll it would cause. However, if it is not opened, the Resistance
cannot control it in the future.
Meanwhile, John meets a new friend named Riley. He shows her his new house but is embarrassed that he has been given a kid's bed. Is Sarah still treating him like a child? Sarah lets Riley stay to prove that is not the case, but is suspicious of John's new friend.
The next day, Greenway has a change of heart and prepares to reactivate the plant. But as Sarah watches, she notices that the scar on Greenway's arm is gone. The person in front of her is a Series 888 Terminator-Infiltrator!
Derek investigates Greenway's house, only to find the real Greenway hanging from the ceiling in a supposed suicide. The Terminator works to overload the reactor but Cameron and Sarah eventually defeat it, with some belated help from Derek, after a frantic fight.
As a result of the chaos, a representative from Automite Systems comes to take control of the plant, announcing that the corporation will be installing artificial intelligences to "eliminate the possibility of human error". After 'his' speech, he gets into his car and morphs into the T-1001, Catherine Weaver.
Later, Sarah notices a blood trail in the new house and follows it to the basement. A list is scrawled on the wall in blood, of places, people and targets connected to Skynet, left by the dead resistance fighter. The team look to have hit the jackpot with the list.
Does it even matter if Catherine Weaver is initiating the first phase of Skynet at the nuclear plant? Who is Weaver exactly, and is her company using the Turk for good, or for evil?