Joanna Drayton, a young white woman, returns to her liberal upper-class American home with John Prentice, an African American doctor whom she has known for a brief period but with whom she has fallen deeply in love. The couple's desire to marry faces immediate challenges, not from the external world as much as from their own families. Joanna's parents, while progressive and ostensibly supportive of racial equality, are taken aback by the suddenness of their daughter's engagement and the racial dynamics it implies. They are forced to confront their own prejudices and the societal pressures of the 1960s America.

The film delves into the complexities of interracial marriage through the lens of a single day, during which John has also placed his own condition: if the parents do not approve of the union, he will leave Joanna. This ultimatum sets the stage for a dinner that is as much a test of personal convictions as it is of societal norms. The parents' internal struggle is intensified by the arrival of John's own parents, who are equally shocked and have their own reservations about the marriage. The contrasting generational and cultural perspectives on race, love, and acceptance are explored through this intimate family gathering, setting the scene for a profound exploration of themes that were both revolutionary and deeply challenging for the time.