After another in a series of mock suicides staged by 20-year-old Harold Chasen fails to gain the attention he craves from his wealthy, socialite mother, the sullen young man stages a bloody scene in her bathroom, finally driving her to send him to a psychiatrist. During a therapy session, Harold explains that he finds "fun" in attending funerals. Soon after, Harold buys a hearse and goes to a funeral for a stranger, where he spots another casual observer, the 79-year-old Maude. At home that night, Mrs. Chasen, outraged by Harold's "amateur theatrics," sends him to his uncle, Gen. Victor Ball, a one-armed veteran who urges him to join the military and then salutes a portrait of his hero, Nathan Hale, using his mechanically rigged sleeve. Days later, after Harold fails to shake his imperturbable mother by floating face down in her lap pool, Mrs. Chasen announces that Harold must assume "adult responsibilities" by marrying and arranges for a series of dates. During a funeral for another stranger, Maude offers Harold licorice and then suggests that the deceased, who was 80, died at the perfect age. As the mourners exit the church, the affable Maude introduces herself, tells Harold they will be "great friends" and then steals the minister's car. Later, while Mrs. Chasen recites the dating service survey question "Do you have ups and downs without obvious reason?" Harold fakes shooting himself in the head. At the end of the next funeral Harold attends, Maude steals his hearse for a joy ride, then turns the wheel over to him after he informs her that it is his vehicle. Harold then drives Maude to her home, a converted railroad car full of art and memorabilia. Later, at the psychiatrist's office, Harold admits that he might have one friend, Maude. During his first date with Candy Gulf at the Chasen home, Harold pretends to set himself on fire within sight of young woman, who flees the house in terror. On his next visit to Maude, he finds his friend modeling in the nude for ice sculptor Glaucus. After he agrees with her that the nudity is permissible, Maude shows Harold her paintings, sculpture and “olfactory machine,” demonstrating it with a scent called "Snow on 42nd Street." Entranced by Maude's creativity and her insistence on experiencing something new each day, Harold shares with her his favorite activities: watching building demolitions and picnicking at a metal junkyard. Later, at a nursery, Maude explains that she likes to watch things grow and picks a tall solitary sunflower as her favorite flower. After Harold, in turn, chooses a ground cover daisy, saying that all daisies are alike, Maude notes observable differences between them. She advises him that all humans are special; the problem lies in the fact that they allow themselves to be treated all the same. On another outing, Maude, in her zeal, drives over a curb to show Harold a tree being suffocated by the city's smog. When the car is ticketed by police officers, Harold and Maude steal a different vehicle and race through a stop sign, defying the awe-struck police. Later at her home, Maude reminisces metaphorically about her past as a political protestor and explains that now she attempts more idiosyncratic strategies toward change. After playing a song on her player piano for him, Maude gives Harold a banjo. Harold returns home to find his mother has replaced his hearse with a new Jaguar sports car, which he quickly transforms into a mini-hearse with the help of a blowtorch. Days later, when Harold and Maude rush through a tollbooth while delivering the smog-ridden tree to its new home, a motorcycle officer pulls them over. Maude speeds off during the officer's interrogation and drives around in circles until the motorcycle breaks down. Later, when the same officer pulls them over again and reads a list of offenses, Maude and Harold steal his motorcycle. The officer aims his gun at them, but finds his efforts foiled by his unloaded gun. After sharing a hashish pipe at Maude's home, Harold admits that he has not lived, but does enjoy dying and recounts his first "death:" After a school physics lab experiment blows a hole in floor, police mistakenly report to Mrs. Chasen that her son has died in the explosion. Seeing his mother faint and relishing her attention, Harold decides to continue dying. Maude enthusiastically coaches Harold to live in the present and begins to waltz with him. Days later, during a date with Edith Phern, Harold, who has placed a fake plastic arm in the sleeve of his jacket, takes out a meat cleaver and chops off his hand arm, sending Edith fleeing from the room. Learning that his determined mother plans to induct him into the military, Harold and Maude scheme to foil her. Asking Victor to take a walk, Harold endures a minutely detailed account of his uncle's war adventures during another military pep talk. Harold then excitedly enumerates ways to kill and finally reveals a shrunken head, asking if Victor keeps souvenirs. When Maude suddenly appears carrying a peace sign and grabs the head, Harold pretends to start a brawl with her and pushes the elderly woman down a hole in the stone landing. A shocked Victor is convinced Harold killed the protestor and stops talking about the young man's induction. At the close of the day, Harold tells Maude she is beautiful and holds her hand, revealing a number tattoo indicating that she is a Holocaust survivor. During a date with actress Sunshine Doré, Harold performs a mock hara-kiri, but instead of being shocked, the actress recites the suicide scene from "Romeo and Juliet," pretends to stab herself and falls to Harold's side. That night, as Harold gives Maude a gift with the inscription "Harold loves Maude," she throws it in the sea, explaining with a smile that she will always know where it is. After spending the night with Maude, an ebullient Harold announces to his mother that he is marrying her and shows Mrs. Chasen Maude's picture. Horrified by their age difference, Mrs. Chasen sends Harold to see Victor and the psychiatrist, who caution him against the marriage. Finally, Harold is sent to a priest, who suggests that the idea of Harold "commingling" his "firm" body with the elderly woman is perverse. On Maude's 80th birthday, Harold fills her room with paper sunflowers and plans to propose to her, but Maude announces that she has taken enough sleeping tablets to kill her by midnight and wishes him farewell. Harold screams in outrage and calls for an ambulance. On the way to the hospital, as he professes his love to her, Maude looks on approvingly and suggests that Harold "go love some more." A grief-stricken Harold races from the hospital after Maude dies. When his car careens over an ocean cliff, Harold, standing high above on the cliff's edge, plucks at his banjo and skips to the music, celebrating life as Maude would have wanted.