It is 1986, and we meet Bernard Berkman, an increasingly arrogant novelist whose once-bright career has dimmed significantly, leaving him unable to secure an agent for his work. Meanwhile, his wife, Joan, has recently begun to gain considerable acclaim for her own writing, which only fuels the existing tension in their marriage.

In a crucial moment, Bernard and Joan reveal to their two sons—Walt, who is 16, and Frank, who is just 12—that they have decided to separate. Bernard moves to a rental house just across Prospect Park, while the couple agrees on joint custody, aiming to share equal time with their children. However, their relationship turns combative, exacerbating the situation.

As time goes on, Joan starts a romantic relationship with Ivan, Frank’s tennis instructor, while Bernard finds solace in the company of Lili, one of his students at the new residence. The boys find themselves caught in the middle of their parents’ conflicts, choosing sides in the escalating battle: Frank aligns himself with their mother, and Walt, looking up to his father, sides with Bernard, blaming Joan for the upheaval.

Both brothers exhibit signs of distress caused by the divorce, showcasing their internal turmoil in markedly different ways. Frank, overwhelmed by the situation, begins to engage in risky behaviors at school, including drinking beer and mimicking Ivan’s characteristics, further complicating his emotional state. Walt, on the other hand, idolizes his father, attempting to emulate his actions, which leads to the deterioration of his relationship with Sophie, his girlfriend. After performing at his school’s talent show, where he falsely claims to have written “Hey You” by Pink Floyd, he garners applause from peers and family. However, when the truth comes out, the fallout draws the school’s attention, necessitating a meeting with Bernard and Joan regarding Walt’s behavior. It’s agreed that Walt should seek therapy to address his struggles.

During therapy, Walt begins to view his life more objectively, free from his father’s biases. When prompted for a happy memory, he recalls how his mother used to take him to see the awe-inspiring yet frightening giant squid and whale exhibit at the American Museum of Natural History. The memory evolves from fear to fondness as they discuss it together at home, highlighting Joan’s nurturing role since Bernard’s presence often felt lacking.

The tension reaches a boiling point with a fierce argument between Bernard and Joan about custody, which culminates in Bernard collapsing outside their home. After being rushed to the hospital, Bernard requests Walt to remain by his side, but in a poignant moment of realization, Walt chooses to visit the Natural History Museum instead. The film concludes with him standing in front of the exhibit he once feared but can now fully face, symbolizing his growth and newfound understanding of his family dynamics.