While living a tranquil existence on the island of Plymouth, local fisherman Baker Dill experiences unexplainable and bizarre visions. He spends his days aboard his fishing boat, Serenity, alongside his companion Duke, tirelessly hunting a formidable tuna he has named "the beast." Day after day, Baker returns from his fishing expeditions disappointed and empty-handed. In the midst of this, he also engages in a romantic relationship with the local woman Constance.
The quietude of Baker's life is interrupted when his ex-wife Karen arrives unexpectedly. Calling him John Mason, she shares her tragic tale of abuse at the hands of her husband Frank. Karen describes how both she and their son Patrick feel frightened during her altercations with Frank, who creates an oppressive atmosphere at home. She entices Baker with the dark proposition of murdering Frank, yet initially, Baker dismisses the idea with a laugh.
Frank plans a visit to the island to spend time with Karen, and in a twist of fate, he offers Baker $10,000 for a boat ride. Faced with the need to repair his boat, Baker reluctantly accepts the offer. On their excursion, Frank shares the puzzling detail about how Patrick spends hours immersed in a video game centered on fishing. After a tense encounter with a shark during the trip, the trio returns to shore, disappointing Karen.
Later that evening, Karen seduces Baker, and their passionate encounter leads to an agreement: Baker wants to meet Patrick first before accepting her proposal to eliminate Frank. As the story unfolds, Baker discovers he shares a unique telepathic bond with his son Patrick. Motivated by this connection, he decides to shift his focus from pursuing the giant tuna named "Justice" to aiding Karen and Patrick.
The plot thickens when businessman Reid Miller approaches Baker, revealing his affiliation with a fishing equipment company and offering him a complimentary fish tracker. However, Reid's unexpected revelations throw Baker for a loop; he learns that he is actually a character in a video game designed by Patrick. The game has transformed Baker's narrative, pushing him towards thoughts of violence against Frank rather than his original goal of fishing.
Amidst this chaotic realization, Baker uncovers a critical rule: no one dies on the island. This introduces a sense of foreboding as he recognizes that the island may be an isolated realm. It becomes painfully clear that he is ensnared within a game. His social circle appears to be interconnected with the game's logic, continually placing obstacles in his path. For instance, Duke conspires to break Frank's hand to keep him from sailing with Baker the next day.
As the lines between reality and gaming blur, the scenes of Patrick playing the game become crucial—not as flashbacks, but as parallel events playing out simultaneously. It's revealed that the true Baker perished in military service, and now his son has crafted a fishing game to fulfill his fantasy of confronting his abusive stepfather. In a climactic moment, Baker communicates with Patrick through the game's coding, ultimately deciding to honor his son's wish to eliminate Frank.
Karen, meanwhile, cunningly seduces Frank again, getting him heavily intoxicated before coaxing him back onto the boat with Baker. As Baker finally throws Frank overboard, a tense confrontation unfolds as Patrick readies himself to face his stepfather’s long-standing abuse. The film culminates in an emotional reunion, as Patrick integrates himself into the game, reuniting with his father in a poignant ending.
