No. 6 learns of an assassination plot against the retiring No. 2 and fights to prevent it.
It may seem against character for No. 6 to help his captors, but this episode seems to be a case of the good of the many outweighing the good of the few. But is his behavior so altruistic? Yes, he works for the benefit of the Village, but isn’t he also undermining the system that entraps him?