In 1928, aging and lonely New York millionaire Samuel Fulton [Charles Coburn] decides to leave his fortune to the family of the late Millicent Blaisdell [Piper Laurie], the only woman he ever loved but who did not return his feelings. He explains to his lawyer Edward Norton [Frank Ferguson] that losing Millicent spurred him to become a wealthy man, and to ensure the money is handled wisely, he heads to their small Vermont town, renting a room in their house under the alias John Smith.
Roberta Blaisdell [Gigi Perreau] welcomes him with warmth, and the Blaisdells come across as a happy, proud clan who value character over material goods despite their modest means. Father Charles [Larry Gates] has taught the family to keep their feet on the ground, while mother Harriet [Lynn Bari] longs for daughter Millicent “Millie” [Piper Laurie] to marry Carl Pennock [Skip Homeier], a wealthy, snobbish young man who can buy Millie everything Harriet never had. Millie, however, isn’t keen on Carl and dreams of a life with local soda jerk Dan Stebbins [Rock Hudson].
One night, Millie and Dan announce their engagement, which upsets Harriet. Shortly after, Norton arrives with startling news: the family has inherited $100,000 from an anonymous benefactor. Overnight, the Blaisdells shed their humble lifestyle and chase the trappings of the upper class. Howard Blaisdell [William Reynolds], the eldest son, plunges into gambling and debt, and Samuel ends up helping him. Dan, feeling he can’t live up to Millie’s new world, breaks off the engagement. Millie reluctantly resumes dating Carl to appease her mother.
Samuel steps in to protect Millie and Howard during a raid, a move that lands him in jail. Harriet misreads his presence as a threat to the family’s delicate image and remains blind to the true reason for his imprisonment. Dan stands by him, hoping to leave town and pursue a real career. To avoid losing Millie and Dan, Samuel arranges a meeting at the cinema, where a heated confrontation unfolds and Millie voices her contempt for their sudden wealth. Yet her confession also draws empathetic attention from theatregoers who sense a budding connection between them.
During a grand social affair at the Blaisdell house, Harriet overhears gossip and pressures Millie to announce her engagement to Carl, even as the family’s finances remain unstable. Charles admits his own losses, underscoring that the Blaisdells aren’t equipped to manage a fortune. Norton refuses to lend them money, and Charles pleads with the Pennocks for help, but they refuse, ending Carl and Millie’s engagement. Faced with the return to their former life, the Blaisdells revert to their old ways, and Millie and Dan’s engagement is rekindled.
In the final twist, Roberta reveals that Samuel’s alias John has won the first prize at an art show, a secret Roberta secretly entered on his behalf. Samuel steps away from the Blaisdell household to avoid press attention, quietly realizing that the family now sees him as the grandfather he could have become.
