Amy realizes that in order to back up her story, she needs to keep Nick on her side. She tells her story in such a way as to cover up as many inconsistencies as possible. Amy's experience also has financial benefits: her parents are offered a contract for a new Amazing Amy book, and Amy begins working on a memoir, which she plans to call Amazing.
Meanwhile, Nick is surprised at an invitation to a meeting with Detective Boney. At the meeting, Boney tells him that she believes his story about being framed and that she is frustrated that she cannot prove this theory. Boney explains that the police consider the case resolved, and that the only way she would be able to move forward is if Nick can provide her with evidence.
Nick finds the frozen vomit and throws it out, but Amy continues to feel confident that she can control him. Unbeknownst to Nick, she is laying another plan in order to trap him once and for all.
Nick continues to meet with Detective Boney and Margo, in hopes that the three of them can find a way to reveal the truth about Amy. It seems, however, that the rest of the world is moving on. Nick's father dies.
The next day, Nick begins writing a book telling his side of the story, and revealing the truth about Amy. When Nick has completed the manuscript, twenty weeks after Amy's return, he shows it to his wife. Amy responds by revealing that she is pregnant.
Nick is shocked by Amy's pregnancy, but figures out that she must have used the semen from their fertility treatments, and secretly had herself inseminated. Nick is immediately attached to their future child, and afraid that if he doesn't follow Amy's instructions, he will never have a relationship with his son. Nick deletes his manuscript, and tells Detective Boney that he will no longer pursue the case against Amy. When Nick tells Margo about the baby, Margo is devastated that Nick will now be stuck with Amy forever. Nick, however, finds acceptance and peace in the reality of his fate.
The novel ends the night before Amy's due date, which is her sixth wedding anniversary. She feels secure that Nick will remain devoted to her, but she also feels uneasy knowing that, deep down, her husband sees her as a terrible person.
Amy remains shrewd and plotting to the very end. She sees an opportunity to derive financial profit from her apparent abduction by writing a book. The fact that she rapidly gets a lucrative book contract reveals how successful she has been at crafting a story that engages the public imagination. While her book will be presented as a memoir, much of it will be fiction. This continues the theme of the unreliability of narratives and storytellers, represented by the diary and the misleading structure of the novel's first section. All of these elements, as well as the media coverage and reports given by both Nick and Amy, have demonstrated the often blurry line between reality and deception.
Amy's most calculated move, however, is her insemination with Nick's frozen sperm. She knows that when she announces her pregnancy she will have the ultimate bargaining chip to use against Nick and can thus ensure that he will always cooperate in her plans. Amy's willingness to use pregnancy and an eventual child as pawns in her game reveals the ultimate depths of her calculating nature. This choice also demonstrates how the novel unsettles gender roles. Typically, women display a strong protective and nurturing side. Amy, however, is only interested in a baby if it benefits her, and it is Nick who immediately feels attached to his future son.
Amy's pregnancy arguably causes her to win in the complicated power struggle that she and Nick have been engaging in. Up until that point, Nick had been trying to find a way to tell his own story and reveal the truth. When Nick began writing his version of what happened, he symbolically reclaimed a sense of power and control. His work as a writer had been a big part of his identity, and something that made him feel good about himself. After he lost his job, his vulnerability and lack of self-esteem made him more susceptible to Amy's schemes. By returning to writing, he demonstrates that he has regained his sense of self-worth, and will no longer be manipulated. His writing of the book parallels both Amy's writing of the fake diary and the largely fabricated memoir. His book is a counternarrative, telling his side of the story.
Ultimately, however, Nick prioritizes having a relationship with his future child over this form of justice. He deletes his manuscript, symbolically signalling an acquiescence to Amy's version of events. Nick will not fight any longer, and he will allow her to present whatever version of the truth that she wants to. This decision on Nick's part might be seen as a defeat, in that Amy will get away with her actions and never be punished for them or be shown to be the terrible person that she actually is.
On the other hand, Nick might be seen as the stronger person because of the decision he makes. Unlike Amy, he cares about the well-being of their child, and the most important thing is for him to have a relationship with his son. Because Nick has grown up without a father he could look up to, he knows how traumatic this can be. Nick is willing to make sacrifices for the people he loves, something Amy was never able to do.
The novel's final section is ambiguous as to who has won the power struggle. Amy is being lavished with attention by Nick, and it seems that she has gotten everything she wanted. However, under the apparently loving exterior, Nick feels disgust and pity towards her. Since Amy has orchestrated a world where truth no longer matters, she is doomed to live a lie forever. Her husband will never love her, no matter if he pretends to. Amy's obsessive need to have the final word at the end of the narrative suggests that she is struggling to maintain a sense of power and control, but that her victory actually feels hollow.