Wright stumbles through the remains of Los Angeles and runs into a young Kyle Reese (Anton Yelchin) and his quiet companion Star (Jadgrace Berry). They save Wright from the attack of a T-600 Terminator only to get taken prisoner a bit later. Marcus finds a downed Resistance pilot — Blair Williams (Moon Bloodgood) and the two set off for Connor's base...
Through the course of the movie, we discover that Wright himself is unknowingly one of this new type of Terminator. Skynet is testing the new model as an infiltration unit that can get inside Resistance cells and with a command from the central computer destroy anything and everything around him. It would be devastating for Skynet to have that kind of capability. No one could be trusted and the Resistance would fall apart.
At the end of the film, the Resistance and Wright attack a Skynet base to try and free Reese and some of the other prisoners before a massive attack on the base can be initiated by the Resistance high command. Though they free the prisoners, Connor gets injured and the high command is destroyed, leaving Connor in charge. To save Connor's life, Wright gives up his own supercharged heart to be transplanted into Connor's body.
Ultimately it's a great exploration of what makes us human. Are we simply parts of a big machine or more than that? Can a Terminator still have humanity?
So back to the book now... Connor is still recovering from surgery, but he and his lieutenants are directing Resistance members to kill as many "live" Terminators at the Skynet base as they can and collect as many working or repairable guns and ammunition as they can for the inevitable counter-attack from Skynet.
Connor's second in command, Barnes (Common in Terminator Salvation) and Blair are on a secondary mission to find Barnes' brother and give him a proper burial. Reese has been sent out to collect ammunition with a team and Star has stayed behind in camp to help with repairing weapons, which she has turned out to have a gift for.
While Barnes & Blair are away, they discover a data cable leading into the mountains above the ruined base. Thinking it might be a secondary base, they follow the cable until they lose it in the trees, but find a group of people staying in the town of Baker's Hollow. Led by Mayor Daniel Preston and his daughter Hope, the townspeople have struggled to keep a low profile and simply keep their population of 80+ safe, fed, and out of harm's way.