Billy confronts his father at home after leaving Jet Mason’s funeral. Billy lays out a detailed theory: Billy’s father had an affair with Dianne Mason, is Luke Mason’s real father, and helped cover up Emily Mason’s death by staging the pool drowning and giving Luke an alibi. Billy explains that Billy’s mother suspected something terrible, believed Billy’s father might have killed Emily, and eventually left because she feared him.

Billy then accuses his father of killing Jet on Halloween. Billy reconstructs the murder step by step: after learning Dianne voted against him for chief and hearing the company would be sold to Nell Jankowski, Billy’s father used Billy’s hidden spare key to enter Billy’s apartment, took the hammer from Billy’s unused tool kit, entered the Masons’ home through an unsecured side door, and struck Jet multiple times. Billy says Billy’s father took Jet’s phone and hid both phone and hammer at the North Street construction site beneath soon-to-be-poured concrete, then responded to the call in his squad car to appear uninvolved.

To force the truth, Billy produces a gun (borrowed from Henry Lim) and demands a confession. Under threat, Billy’s father admits he killed Jet and says he did it to protect Luke, claiming rage “took over” as it had on the day Emily died. Billy refuses to shoot him, revealing instead that the goal was not a recording but to have a listener hear the confession.

Luke enters and reveals he heard everything through Billy’s phone. Luke erupts at being lied to and at Jet’s death, while Billy insists they can go to the police together and point them to the tool kit as evidence. Billy’s father tries to dismiss the confession as coerced, and Luke seizes on the presence of the gun.

Luke grabs the gun, fires once into the ceiling during Billy’s attempt to stop him, and then chases Billy’s father to the Mason house. As Billy follows, Billy’s father begs Dianne for help at the front door; Dianne, Scott, and Sophia appear inside. Luke shoots Billy’s father at the doorstep, and he collapses dead as the family opens the door and screams.