Shirley MacLaine plays Louisa May Foster, a romantic young woman who realizes she wants to marry for love, and not for money. However, she believes she's a victim of a supernatural curse, as she tends to marry poor men for love, then ends up a neglected wife and a rich widow. To prove her point, all of her four husbands die off after achieving wealth. All four leave her immensely wealthy but intensely unhappy.
In a dream-like pre-credit sequence, a pink coffin is carried down a pink staircase in a pink mansion with Louisa as a black-clad widow following behind. The pallbearers drop the coffin, which sleds down the stairs.
Louisa tries desperately to give away more than $200 million dollars to the U.S. government Internal Revenue Service who believe it an April Fool joke. Louisa ends up as sobbing widow on the couch of an unstable psychiatrist (Robert Cummings). Louisa tries to explain herself and her motivation for giving away all that money which leads into the rest of the story, a primarily romantic flashback with occasional fantasies from Louisa's point of view including a Marnie type aversion to the colour pink.
We meet Louisa as a young, idealistic girl. Her mother (Margaret Dumont) is fixated on money; she is pushing for Louisa to marry Leonard Crawley (Dean Martin), the richest man in town. Louisa loathes Lennie and instead takes up with Edgar Hopper (Dick Van Dyke), an old school friend who inadvertently woos her with his relaxed attitude, lack of ambition, and love of the simple life. Hopper is inspired by the writing of Henry David Thoreau, taking the writer's message of "simplify, simplify!" to heart. Louisa elects to marry Hopper, and they live in a shack, poor but happy (illustrated with a silent movie styled fantasy sequence) until Hopper abandons the simple life for an all-out assault to drive Crawley out of business in Crawleyville. Edgar makes a lot of money while pushing himself to his human limits. He achieves his goal of bankrupting Crawley, but pays the ultimate price and falls dead while chiding "Hard work never hurt anybody!"
After Hopper's death, Louisa is a millionaire. She travels to Paris where she meets Larry Flint (Paul Newman). Avant-garde art dominates Flint's life, including a chimpanzee that paints. One of his projects is a "Sonic Palette", a machine that paints by sound, a "fusion of man and machine -- the only positive statement in art that is being made today!" Louisa falls in love with Flint's attitude of "Money corrupts. Art erupts!" and marries him. She enters into his bohemian lifestyle while renouncing her secret millions. An erotic foreign-film spoof shows the sheet-clad pair making love in progressively smaller bathtubs and on a bed. Flint's minimalist abstracts are just good enough to keep them fed. Louisa idly suggests having the machine paint to Felix Mendelssohn's Spring Song -- thus leading to the creation of a masterpiece. Flint becomes famous by having the machine "paint" more music, and thus increasingly obsessed with all the money coming into his life. He builds more Sonic Palettes to paint a giant work of art, but the machines wind up turning on their creator, which ends up killing him.
Louisa is richer but more depressed. After missing a flight back to the States, she meets an already wealthy magnate named Rod Anderson (Robert Mitchum), who offers her a lift on his jet, Melissa. After discovering the softer, kinder man under the business-magnate veneer he projects, she convinces herself that it might be easier to love a rich man since she can't make him any richer and inadvertently cause his death. To paraphrase Louisa's narrative, it is "like one of those lush budget films where it's all about what she's going to wear next." This fantasy segment is full of Edith Head's over-the-top costumes and ends with Mitchum and MacLaine making love in a huge champagne glass. Despite his happy retreat into marriage, Rod discovers he's actually gotten richer while neglecting his industry. Just as he vows to find out who is responsible for making his company successful WITHOUT him, Louisa discovers Melissa was a prize cow he raised in his youth. Louisa convinces Rod to sell everything and retire to the type of small farm he lived on during his childhood. The good news is that Rod never neglects her. However, a slightly-tipsy Rod makes a fateful mistake by trying to milk his bull, Melrose. The unhappy steer kicks Rod through the barn wall, and leaves Louisa a widow yet again, and now fantastically wealthy.
Louisa wanders the States alone. In a cafe called the Cauliflower Ear in a podunk town, she meets Pinky Benson (Gene Kelly), a customer who charms her with silly dances and rhymes in the manner of Pinky Lee. She learns he's been a performer at the Cauliflower Ear for 14 years. Pinky invites her to come see him perform. She sees that his clown act is tolerated because he doesn't distract from the serving of food or liquor. Louisa is charmed by Pinky's satisfaction with his simple lot in life, seeing it as mirroring her own desires. She marries him. One night, she suggests that Pinky perform without his clown makeup, and suddenly the customers notice his talent. In short order, Pinky becomes a Hollywood movie star. Once again Louisa is neglected by a husband obsessed with fame. An all-pink mansion is among Pinky's obsessions, as is Louisa's appearance at a movie screening in an all-pink chinchilla coat and a pink wig. Pinky's adoring public stampede him at the premiere, trampling him into an early grave (the funeral we see at the beginning of the film).
Louisa has told the psychiatrist her sad tale. He turns and begs her to marry him, just as a familiar-looking janitor comes into the office. In an attempt to lower the psychiatrist's chair that Robert Cummings' character is stuck in, she winds up letting him drop from ceiling-height, knocking him out cold, reviving him by throwing a bucket of water on him. She then turns and makes the happy discovery that the janitor is Leonard Crawley, who has lost everything and is now leading a poor, simple life that she can share. As the doctor comes to, he sees Louisa and Leonard kissing passionately, which causes him to pass out again.
In the end, several years later, we see a happy and no-longer-curse-weary Louisa with several children in a quaint house, while Leonard sits in his running tractor reading Thoreau. The tractor slowly grinds itself into the ground and strikes oil. Thinking her "curse" has finally resurfaced, a devastated Louisa runs to her husband just as a man in coveralls runs up and starts berating Leonard for hitting an underground oil pipe with his tractor. Relieved, Louisa hugs and kisses Leonard as both are showered by the erupting oil.