Ally sells Kai out by turning out to be an FBI informant. She orchestrates the FBI raid shortly before the cult sets out to murder 100 pregnant women as part of Kai's "Night of 100 Tates."
Kai remains in jail for 11 months, where he amasses a following (including a female prison guard who becomes his lover) and plots revenge on Ally.
Ally, meanwhile, becomes something of a celebrity for having defeated Kai and escaped the cult. Shr shrugs off the notoriety and enjoys life with Oz and her new girlfriend. When Beverly, who got off without any charges, visits at the restaurant, Ally maintains that it was Kai who killed Ivy.
Kai calls Ally after hearing that Oz is not his son after all. Ally mocks him and he threatens to come for her and kill her. After this, Ally is inspired to announce her candidacy for Michigan state senator. Kai sees this and decides to put his escape plan in motion.
Kai kills and cuts off the face of one of his followers, who he'd specifically groomed to look just like him, to make it seem like he is dead in prison. He goes to confront Ally at the senatorial debate.
At the debate, Ally confidently pulls it off over her male opponent. Kai interrupts and moves to shoot Ally after giving a long, misogynist speech. When his gun doesn't fire, it's revealed that Kai's lover the prison guard was in cahoots with Ally and gave him a useless weapon.
Ally, smiling, tells Kai that a nasty woman is more dangerous than a humiliated man, contrary to what he said earlier in the season. Beverly steps in to shoot and kill Ally.
Ally wins the senator race, but the closing scene reveals that she is now in (or leading) a cult modeled on Valerie Solanas' SCUM followers.