Shortly after the surrender of Japan, marking the end of World War II, United States Army Sgt. Paul Sutton returns to San Francisco to reunite with his wife Betty, whom he married — following a whirlwind courtship — the day before he departed for the Pacific. The war has left him with emotional scars, and he experiences flashbacks on a regular basis.

Paul's reunion with Betty is strained, especially after he discovers most of the letters he wrote her were set aside unopened. He is determined to make a go of the marriage however, and hopes to establish a new career for himself. Betty insists he continue to sell candy door-to-door, and he sets off to Sacramento. En route, he meets fellow bus passenger Victoria Aragon, a Stanford University graduate student whose Mexican-American family owns a vineyard in the Napa Valley. When he learns the unmarried woman is pregnant by her professor, Paul offers to introduce himself to her very traditionalist family as her husband.

Victoria's father is infuriated, not only that she married a man below her social standing, but without his permission as well. Paul's initial plan to quietly slip away and continue on his journey, leaving Victoria's family to believe he abandoned her, is derailed when her grandfather Don Pedro encourages him to stay and help with the harvest. During the harvest Paul (an orphan) grows closer to the family and learns the joys that come with their tradition, roots, and way of life. Paul and Victoria try to ignore their growing attraction and feelings for each other, but with little success. However Paul's honor prompts him to attempt to salvage his marriage and return home, but when he does he discovers his wife is involved with another man. She has applied for an annulment, to which he happily agrees, and he returns to the Aragon estate to ask Victoria to marry him.

An argument with her angry, and drunk, father leads to a disastrous fire which destroys the vineyard. However Paul remembers one plant that may still have its roots intact and races off to retrieve them and bring them back to the family. The disaster (as well as Paul's bravery and dedication during the fire) has brought Victoria's father to realize his errors. So when Paul returns he accepts him, telling him that this is "his family" and "his roots". The family sets out to replant and rebuild with the help of their newest member.