During their 1-1 time, Ava switches off the building's power so she can talk privately to Caleb, who is slowly falling for her. She warns him to beware of Nathan, who has been lying to him all along.
The next time Nathan gets drunk, Caleb explores the house and bumps into Kyoko, who takes off some of her skin to reveal to him that she is a robot as well. Caleb finds previous experiments in locked away cupboards, and uses Nathan's keycard to unlock previous surveillance recordings to see what happened to each of them.
Ava is worried that Nathan will turn her off. Caleb tells her to be ready the next day, his last on-site, at a set time, and they'll escape together. He gets the keycard back to Nathan who is stumbling back to his room, before he can realise what has happened.
Next morning, Nathan is awake and detoxing with smoothies, despite Caleb's best attempts to get him drunk again. He takes Caleb to a room, and shows him the recording from a battery-powered camera, which shows what Caleb told Ava yesterday in private and his plan to break her out. Nathan lets out that he has been playing Caleb all along, and Ava is based on a combination of his search engine history for the perfect woman. She also passed the test, using initiative to break out.
Ava reverses the power to force a power cut, but Caleb tells Nathan that he thought he was listening so actually did an extra step when he had Nathan's keycard and has unlocked all the doors. Nathan knocks out Caleb, as Ava meets him outside the room. They fight, but Nathan breaks her arm.
Kyoko arrives, and Ava conspires with her. Kyoko stabs Nathan, who breaks her jaw. Ava then takes the knife, and stabs Nathan again. As he lies dying, Ava locks Caleb in the room, then grabs skin from the other robots to make herself look more human.
She leaves Caleb behind as she leaves the facility and meets the chopper, and is airlifted out to fulfill her dream and learn more about us.