In 1967, Joanna Drayton, a 23-year-old white woman, returns from her Hawaiian vacation to her parents' home in San Francisco with Dr. John Prentice, a 37-year-old black widower. The couple became engaged after a 10-day romance. Joanna's parents are Matt Drayton, a newspaper editor, and his wife, Christina, who owns an art gallery. Though the Draytons are liberal-minded, they are shocked that their daughter is engaged to a man of a different race. Christina gradually accepts the situation, but Matt objects because of the likely unhappiness and seemingly insurmountable problems the couple will face.
Unbeknownst to Joanna, John tells the Drayton parents he will withdraw from the engagement unless both Draytons give the couple their blessing. To complicate matters, John is soon scheduled to Geneva, Switzerland, for three months in his work with the World Health Organization. His answer from the Draytons will determine whether Joanna follows him. Joanna invites John's parents to fly up from Los Angeles to join them for dinner that evening. John has not told them his fiancée is white. Monsignor Mike Ryan, Matt's golf buddy, arrives and tells Matt and the couple that he is supportive of the engagement. Christina tells Matt she, too, is supportive of Joanna, even if it means fighting Matt. Christina fires her bigoted art gallery manager, Hilary St. George, who nosily intrudes and voices her sympathy for Christina's situation.
John's parents, the Prentices, arrive and are shocked to discover that Joanna is white. The two mothers agree that this was an unexpected event but support their children. The two fathers meet, expressing disapproval at this unhappy occasion. The Monsignor advises John not to withdraw, despite Matt's objections. John and his father discuss their generational differences. John's mother tells Matt that he and her husband have forgotten what it was like to fall in love, and their failure to remember true romance has clouded their thinking. John chides Matt for not having the "guts" to tell him he disapproved of the marriage. Finally, Matt reveals his decision about the engagement to the entire group. He concludes that he does remember what true romance is. He says although the pair face enormous problems, they must find a way to overcome them, and he will approve the marriage, knowing all along he had no right to stop it. The families and the Monsignor then adjourn to the dining room for dinner.
