A film instructor and self-help coach, known as “the Maestro,” instructs a workshop titled, “Star Therapy,” teaching others how to be the hero of their lives by starring in their own films. During class, the Maestro presents a case study about a former student, Denis Byrd, who tried to break into stardom and become his own life’s leading man. The summer before Denis enters college, his mother is suicidal after realizing that her husband, Dr. Byrd, is a philanderer. Denis attempts to calm her, but she prefers to be comforted by her oldest and favorite son, James Byrd. After earning fame in California for his philosophy about spartan living, James returns home and teaches a summer college course on the subject, titled Spartanetics 101, for male students only. However, Denis has doubts about his brother’s “unusual” ascetic beliefs. One evening, James prepares to introduce the family to his girl friend, Kristina, whom he has been rehabilitating through spartan habits. Formerly, Kristina was an impulsive eater and led a promiscuous life that included an erotic stage act with a rabbit hand puppet, named Bunny. Before arriving, James instructs Kristina that the dinner is her initial test, and she should prove her newfound discipline by resisting food. At the first sight of his brother’s attractive girl friend, Denis is infatuated. During the meal, James announces that he and Kristina are going to be married, and Mrs. Byrd immediately plans the engagement party. When Kristina eats a piece of beef by mistake and appears to choke, James saves her. Denis watches with jealousy, longing to be the hero of the family. The next day, Denis offers to help his mother prepare for a divorce. At an attorney’s office, he discovers that marital infidelity should be captured with pictures to ensure a better settlement. For three weeks, he sits in a tree with a view of his father’s medical practice and spies on Dr. Byrd and his Swedish nurse as they frolic in the office at night. However, he is never able to capture an incriminating photograph. As Denis becomes bored with the project, the Maestro appears in the tree, diagnosing Denis as “a peeping Tom” and “a bit player.” The Maestro offers to help and gives Denis his business card. Meanwhile, Kristina carefully prepares a picnic of organic food for James and his class to take on a hike. However, James destroys the lunch and screams that his students must forage for food in nature. Afterward, Denis consoles Kristina by taking her to a fast food restaurant, where she delights in eating a hamburger. When Kristina returns to the Byrd residence that evening, James smells the forbidden meal on her fingers and declares that the engagement will be cancelled unless she passes a series of temptation tests. Meanwhile, during the first treatment with the Maestro, Denis is instructed to make a film about his life and cast himself as the star. After the Maestro screens the rough cut, he concludes that the footage is boring and encourages Denis to find a story in his life that will sell tickets. Denis decides to capture his father’s infidelity on film. Elsewhere, Kristina passes the first four tests of her “temptation marathon” by not giving in to alcohol, smoking, drugs. and junk food. For the final challenge, resisting sex, she is instructed to appear at the hangout of a motorcycle gang in seductive attire. Denis overhears the plan and follows Kristina to the hangout. When one of the gang members threatens to assault Kristina, Denis rescues her. As soon as Kristina is out of harm’s way, Denis argues that she should not change herself to satisfy James’s deranged principles, but Kristina still wants to marry James and disregards the advice. At the Byrd residence, James writes notes to his students, inviting them to the campsite at midnight. One of the notes is blown by a gust of wind and accidently lands on Kristina’s pillow. Later that evening, Kristina finds the invitation and believes that James wants to reconcile with her after she passed the temptation challenges. When she arrives at the campsite, she sees James teaching the young men about sex by having them practice with each other. Kristina perceives their activity as homosexual behavior, and runs back to the house upset. Meanwhile, Denis persuades a security guard to let him break into the medical building, and he catches his father on film seducing a nurse. Back at the house, Denis’s “grandma” sets up her own home movie camera for the next day’s engagement party and borrows extra film from Denis. That night, Denis finds Kristina distraught and arguing with Bunny, the rabbit hand puppet. Kristina asks Denis to kiss her, and they make love. As the engagement party begins the next day, Kristina swallows a handful of Mrs. Byrd’s sleeping pills and becomes possessed by the rabbit puppet. She distributes publicity photographs of her explicit stage act at the Pussycat Lounge to party guests. While James denounces Kristina in front of everyone, Denis leads her to Dr. Byrd’s office for medical care. Before Dr. Byrd pumps her stomach, he orders Denis to wait outside. However, Denis is distrustful of his womanizing father, so he keeps an eye on Kristina from the tree near the window. After the procedure, Dr. Byrd guides the frail young woman to the entrance of the building. In the meantime, James arrives, sees Kristina with his father, and aims a gun at her. Fleeing into the street, Kristina is hit by an ambulance and presumed dead. Denis, who falls from the tree and knocks his head, is unable to save her. After recovering from the incident, Denis packs for his first year of college and says goodbye to his family at the train station. Later, at the Byrd residence, the family cries while they watch grandma’s home movie of Kristina’s strange behavior at the party. Suddenly, the reel cuts to Denis’ footage of his father having sex with a nurse, giving Mrs. Byrd the evidence she needs. Waiting at the station alone, Denis acknowledges that the Maestro was right, he is “an extra in his own life.” Unexpectedly, Kristina appears, explaining that she survived the accident after the ambulance rushed her to the hospital. Happily reunited, Kristina and Denis take the trip to college together.