In a college setting, graduate student Theresa Dunn experiences vivid daydreams about her professor, Martin Engle, while he reads her essay in class. As she becomes his assistant, Theresa opens up about the challenges she faced growing up, including having polio at six and undergoing surgery at eleven, which left her with scars and chronic back pain. Seeking solace from Martin, she provocatively expresses a desire for seduction, to which he responds that a teacher-student relationship is morally and legally wrong, yet the two cannot resist each other and share a passionate encounter in his office.
Returning home, we discover Theresa lives with her devout Catholic family in the suburbs. Her divorced sister, Katherine, a flight attendant, visits during a layover and confides in Theresa about her complicated romantic life; she is pregnant, uncertain of the father, and planning to go to Puerto Rico for an abortion.
That evening, Theresa participates in a class meant to prepare her for teaching deaf children. Post-class, she indulges in fantasies of winning a figure skating medal, with Martin congratulating her. The following day, Martin dashes her hopes by ridiculing the Christmas gift she gave him and says he will see her after the holidays. Alone on New Year's Eve, she receives a call from Katherine, who has swiftly married a man she barely knows.
As the semester resumes, Martin reprimands Theresa for calling his home, which leads her to seduce him again. Meanwhile, Katherine introduces her new husband, Barney, to the family. A phone call interrupts their family gathering, and Theresa rushes off to meet Martin again. After their rendezvous, she inquires why they maintain a cold distance post-intimacy, and he reveals his inability to engage with women afterward.
The following morning, Theresa's younger sister, Brigid, shares the news of her second pregnancy, causing tensions to rise during a family dinner. Mr. Dunn, their father [Richard Kiley], reminisces about his mother and her perfect sons, prompting Theresa to remind him about their deceased sister, Maureen, which angers him.
In the final moments of her teaching class, Theresa feels the weight of loneliness as two classmates celebrate their marriage. Feeling disconnected, she slips out quietly. Later, while assisting Martin in packing for the summer, he ends their affair, leaving her fantasizing about a tragic accident with his car that would land her in the hospital.
After a night out, she impulsively visits Katherine's apartment, where she engages in casual drug use while watching adult films with her siblings and their partners. The next morning leads to an explosive confrontation with her father about her whereabouts. Frustrated, Theresa relocates to an apartment just below Katherine and Barney's.
The following week, she starts her new job teaching deaf children while exploring nightlife in bars and clubs. During one evening, she meets Tony, a hustler, but their spark fizzles when he leaves with another woman. On the last day of summer school, she makes plans to spend time with a student’s sibling but becomes involved in the mother’s welfare issues. As school resumes, the family welcomes James [William Atherton], the welfare officer, who begins dating Theresa— much to her family's approval due to his Catholic background.
However, her relationship with James becomes complicated, particularly when her tumultuous past with Tony resurfaces. Unable to connect, she often escapes into alcohol and drugs, eventually leading to a confrontation with Tony when he appears in her apartment after she angrily dismisses him.
As the holidays approach, Theresa grapples with family pressures and the fear of sharing her own family life, leading to tumultuous encounters with her father. On New Year's Eve, during a bath, Tony attempts to break into her apartment, prompting a call to the police. At the same time, Gary, a troubled individual, enters the bar scene, struggling with his own demons.
As midnight strikes, Theresa's encounter with Gary takes a dark twist that culminates in tragedy. Their brief moments of connection shatter into a violent climax, leading to an unimaginable conclusion— leaving Theresa's lifeless body behind in her apartment, marking a devastating end to her complex journey of desire, fear, and self-discovery.
