D-503 doesn’t sleep that night. He discovers that his head is wrapped in a steel band. Furious with U for informing the authorities of his and I-330’s plans, D-503 resolves to murder her to show I-330 that she was the one that betrayed the mission—not him. D-503 finds a steel rod in his room. He carries it downstairs, but U isn’t at her monitor’s desk. He goes outside and finds chaos all around him. He sees a flag in the air bearing the message “Down with the machines! Down with the Operation.” He sees a young boy terrified and running away from something and realizes that U must be at school, at her other job. He tries to board the subterranean rail to search for her, but someone tells him it’s not running today. He is accosted by several post-Operation ciphers who try to force him to join them in receiving the Operation. He escapes and returns home.
D-503 frequently associates U with loyalty to the One State, so murdering her would allow D-503 to prove that he is still loyal to both I-330 and to MEPHI. Further, when D-503 flees from the post-Operation ciphers, it shows that, despite all the misfortune and chaos that I-300 has brought into his life, his desire for her is too strong for him to betray her by undergoing the Operation and becoming a machine of the collective One State.
U is still not at her desk. D-503 returns to his room. At 21:00, U walks in. D-503 looks at the steel rod on the table and presses the button to lower his blinds, even though he hasn’t received permission to do so. U runs to the door to try to escape, but D-503 cuts her off. U moves to the bed and takes off her unif, and D-503 realizes that she thinks he lowered his blinds so they could have sex. D-503 begins to laugh. The telephone rings, He picks it up and is instructed to report to the Benefactor immediately. U admits that it was she who reported MEPHI, though she didn’t give them I-330’s name, seemingly because she thought it would make D-503 stop loving her, though she has difficult articulating this fully.
U’s assumption that D-503 lowered the blinds so they could have sex shows that it was her romantic desire for D-503 that motivated her decision to betray MEPHI—not just her loyalty to the One State. The fact that she failed to give the Guardians I-330’s name specifically—something that would crush D-503—further underscores this point. U seems to be ashamed and embarrassed that her actions were motivated by irrational emotions, which is why she has difficulty articulating her thought process to D-503.