In a rural
New Mexican town in 1989, reclusive gym manager Lou navigates relationships with her sister Beth, Beth's husband JJ, and flirtatious friend Daisy. One night while at the gym, Lou is approached by FBI agents in search of information about Lou's estranged father, Lou Sr., and his criminal ties. Shortly after, Lou meets Jackie, a bisexual bodybuilder staying in town while preparing for a competition in Las Vegas. Lou offers Jackie
steroids to enhance her training and though she initially refuses, Jackie agrees. After a night of sex, Jackie and Lou move in together. They fall in love over the following weeks as Jackie uses increasingly high doses of steroids during her training. Jackie and Lou attend an awkward dinner with JJ and Beth, during which Lou threatens JJ over his abusive behavior towards Beth. In retaliation, JJ reveals he and Jackie had sex on her first night in town in exchange for a waitressing position at Lou Sr.'s gun range. Disgusted and angry, Lou tells Jackie that she wants to kill JJ because of his abuse of Beth, who is the only reason Lou hasn't left town. The next day, Beth is hospitalized due to severe abuse inflicted by JJ. At her bedside, Lou Sr. promises to protect Beth and deal with JJ. Unable to contain her rage due to steroid use, Jackie secretly breaks into Beth and JJ's home and brutally beats the latter to death. Lou discovers JJ's body, and fearing Jackie will be arrested, plots to frame her father for the murder. With Jackie's help, Lou loads JJ's body into his car and drives it over a cliff into a ravine revealed to be a disposal site for the bodies of Lou Sr.'s various criminal enemies. Lou lights the car on fire, creating a massive smoke plume that she knows will attract the authorities to the site the following morning. The next day, Lou returns to JJ and Beth's home to clean up evidence of the murder while Jackie continues her steroid use, growing more agitated. After an argument, Jackie leaves Lou and hitchhikes to Las Vegas for the bodybuilding competition. During her individual routine, Jackie hallucinates vomiting up a fully grown Lou before assaulting another contestant, leading to her arrest. Meanwhile, armed with knowledge of Lou and Jackie's involvement with JJ's murder after spotting the duo out driving the night before, Daisy blackmails Lou into a relationship. After Daisy intercepts Jackie's phone call from jail to Lou, Jackie contacts Lou Sr. to bail her out of jail. After doing so, Lou Sr. coerces Jackie to kill Daisy, the sole person connecting the women to the murder. After shooting Daisy at Lou's apartment, Jackie returns to Lou Sr., only to be knocked unconscious. Lou Sr. calls Lou and tells her that he has arranged for Jackie to take the rap for the deaths of JJ and Daisy, but Lou, who has helped her father kill in the past, announces her intention to cooperate with the FBI investigation if he sets Jackie up. Lou Sr. sends a police officer on his payroll to kill Lou, but she returns fire and kills him before driving to her father's home to rescue Jackie. At Lou Sr.'s manor, Beth, who has learned about her involvement with JJ's death, denounces Lou to her face. Lou finds and frees Jackie, but as they try to escape, Lou Sr. shoots Lou in the leg. Jackie,
having grown to a gigantic size, pins down Lou Sr., and Lou considers killing him before deciding to leave him for the police. Lou and Jackie, back to her normal size, drive off together. The next morning, Lou realizes that Daisy is still alive in the truck bed despite her near-fatal wound. She strangles Daisy and dumps her body in a nearby field while Jackie sleeps. ==Cast==