At the start of the novel, single mother Lily Kincaid (née Bloom) is pondering whether or not to reignite a romance with her high school sweetheart, Atlas Corrigan, weighing her attraction to him against the jealous rage of her ex-husband, Ryle Kincaid. The war in Lily’s heart between these two men has been going on since nearly the beginning of her relationship with Ryle, whose temper, manipulation, and gaslighting often drove her to betray herself in the past. In contrast, her adolescent relationship with Atlas was marked by sweetness and kindness, and throughout Lily’s marriage, Atlas often served as a shelter from the storm as she weathered Ryle’s abuse. Faced with the possibility of a new beginning, Lily is at first frightened and ambivalent about whether or not being with Atlas will be undermined and destroyed by Ryle.  

Throughout the novel, each time Lily’s relationship with Atlas progresses, she faces a confrontation with Ryle. For example, after Lily’s wonderful first date with Atlas, Ryle starts a fight with Lily about their infant daughter Emerson’s middle name, which is an homage to Finding Nemo, a movie significant to Lily and Atlas as teens. And after the first time Atlas and Lily make love as adults, Ryle discovers they are together and goes on a violent rampage, harming both Lily and Atlas. Lily is continually challenged to set firm boundaries with Ryle in order to freely live her life with the man she loves, and it is not until she crosses this threshold that she can do so. Though Lily fears Ryle, as she falls more and more deeply in love with Atlas, she continues to get stronger in her conviction that she deserves a happy life, pushing back more and more vehemently against Ryle’s attempts at control. Finally, with the help of her best friend and Ryle’s sister Allysa, Allysa’s husband and Ryle’s best friend Marshall, and through her fierce love of her daughter Emerson, Lily fully breaks free from Ryle.