The power outages also trigger the building's security system to lock all the doors. During one outage, Ava tells Caleb that Nathan is a liar who cannot be trusted. Caleb grows uncomfortable with Nathan's narcissism, excessive drinking, and crude behaviour towards Kyoko and Ava. He learns that Nathan intends to upgrade Ava, deleting her memory, including interactions with Caleb, and thereby "killing" her current personality in the process. After encouraging Nathan to drink until he has passed out, Caleb steals his security card to gain access to his room and computer. After altering some of Nathan's code, Caleb discovers footage of Nathan interacting with previous android models in disturbing ways, and learns that Kyoko is also an android. Becoming paranoid that he himself may be an android, Caleb goes back to his room and cuts his arm open with his razor to examine his flesh, thus confirming that he is human. At their next meeting, Ava cuts the power. Caleb explains what Nathan is going to do to her and Ava begs for his help. They form a plan: Caleb will get Nathan drunk again and reprogram the security system to open the doors during a power failure instead of locking them. When Ava cuts the power, Caleb and Ava will leave together. Nathan reveals to Caleb that he observed Caleb and Ava's last secret conversation with a battery-powered camera. He says Ava has only pretended to like Caleb so he will help her escape. This, he says, was the real test all along, and by manipulating Caleb so successfully, Ava has demonstrated true intelligence. Ava then proceeds to cut the power. Caleb reveals that he suspected Nathan was watching them and modified the security system the previous day when Nathan was passed out. After seeing Ava leave her confinement on the surveillance camera, Nathan knocks Caleb unconscious and rushes to stop her. With help from Kyoko, Ava stabs and kills Nathan, but in the process he destroys Kyoko and damages Ava. As Nathan bleeds out, Ava enters his private room and repairs herself. She then takes pieces of artificial skin from Nathan's earlier android models to cover her mechanical appearance. She dons a long brunette wig, a white dress, and high-heeled shoes to take on the full appearance of a young human woman. As she leaves the facility she passes the room Caleb is now locked inside, but ignores his screams. Ava escapes to the outside world and is picked up by the helicopter meant to take Caleb home.