Sarah is dreaming. It is 1944 at the Manhattan Project. The nation's top physicists are developing the atomic bomb. Sarah kills them all, hoping to head off the future apocalypse. They come back to life and become metal skeletal Terminators. They all point their weapons at her. She wakes up.
John and Sarah discuss the resistance fighters. Future John sent them back to find the origins of Skynet and they started with Cyberdyne employees. Sarah decides to pay a visit to Tarissa Dyson and see if she recognizes anyone.
At their first day of school, John and Cameron spot a single cryptic 'A' on a graffitied door. At the entrance, Cameron repeatedly sets off the metal detectors – John explains that she has a metal plate in her head. Sarah meets with Tarissa Dyson and she comes up with a name: Andy Goode, one of Miles' interns at Cyberdyne.
The FBI investigates the scene of the murdered resistance team. Agent Simpson thinks the scene is just a drug buy gone bad and marvels as to why Ellison is even there. At the hospital, a heavily gowned and masked Cromartie steals a large quantity of blood.
Sarah finds Andy Goode managing a local cellular store. She gets a crash course on cell phones from him and buys three phones. As she leaves the store, Andy asks her out on a date.
Ellison questions Enrique's nephew, Carlos. Cromartie captures a molecular biologist in a home invasion. John and Cameron give Sarah a report of their first day in school. She tells them about her meeting with Andy Goode and that she has a date with him tonight.
Cromartie shows the biologist an advanced growth formula and convinces him to help him regrow his skin. On their date, Andy shows Sarah the Turk, his automated chess machine. One of Carlos' boys observes the date.
John questions Sarah about the Turk, but she didn't understand most of what she saw or heard. John tells her about the singularity – the time when machines are able to build more advanced versions of themselves. At FBI headquarters, Ellison learns that, inexplicably, one of the dead men has the fingerprints of a four-year-old boy living in Ohio. He asks Simpson for more evidence from the resistance crime scene. He wants to compare the blood. His New Mexico crime scene has blood with no red cells.
The biologist completes the skin-growing solution. He pours it into his bathtub. He is dumbfounded when Cromartie disrobes and reveals his metal endoskeleton.
At the doctor's office, the doctor tells Sarah that she is cancer-free and doesn't even have any risk factors for cancer. At home, Sarah calls Andy. When she leaves, she takes her gun with her.
At school, another cryptic graffiti door message (DAN) upsets one girl in particular. It turns out a student may have slept with a teacher. Cameron's strange attitude and honesty causes tension in the girls' bathroom. When she tries to engage the upset girl in conversation, the girl gets angry and leaves. Sarah meets Andy at the park. His discussion of Turk's apparent intelligence concerns Sarah. The message on the bulletin board has changed (IDAN). Suddenly students begin running outside. There is a jumper on the roof, and it's the girl Cameron spoke to in the bathroom. John attempts to go help her, but Cameron prevents him and the girl jumps to her death.
John is upset that Cameron stopped him from helping the girl, but Sarah believes it was for the best. If he had, he would have attracted undue attention. Cameron tells Sarah that Andy must die. At the biologist's apartment, the FBI finds a dead body in the bloody bathroom. It is missing its eyes. Andy arrives at his house to find it ablaze as Sarah crouches in the bushes nearby.
In a flashback at the biologist's apartment, Cromartie rises from the tub with a new covering of rough skin. The biologist cuts the skin over his eyes and the Terminator's red eyes shine out.