Nader and Simin, a middle-class couple in Tehran, find their marriage at a crossroads. Simin wants to leave Iran to provide better opportunities for their daughter, Termeh, but Nader refuses to leave his elderly father who suffers from Alzheimer's disease. Faced with a deadlock, Simin files for divorce, but the court rejects her plea. Simin moves out, leaving Nader to manage the household and care for his father. Nader hires Razieh, a poor, devout woman, to help with the caregiving. However, Razieh's work creates new tensions, as she wrestles with her own secrets and challenges, particularly related to her volatile husband, Hodjat.

As Nader and Simin's separation intensifies, it sets off a chain of events that brings legal, personal, and moral dilemmas to light. A heated incident results in accusations that entangle both families, leading to accusations of theft, negligence, and much more. Faced with these mounting pressures, each character's moral boundaries are tested. The once clear lines blur, escalating into a series of confrontations and legal wranglings. The situation becomes a complex exploration of truth, justice, and the intricate fabric of social and familial obligations in contemporary Iran, with lasting implications for everyone involved.