Benjamin Braddock, a recent college graduate, sits perfectly still on his bed in the comfortable Southern California home of his parents, wearing a diving suit. His solitary contemplation is interrupted by his dad, Mr. Braddock, who asks why he isn’t coming downstairs to show off the diving suit, his graduation present, as he was asked. It is Benjamin’s graduation party, and he must come show his parent’s friends a little courtesy. Benjamin asks to be left alone, because he has things on his mind. They are joined by Benjamin’s mom, Mrs. Braddock, and by Mr. Robinson, Mr. Braddock’s business partner, who heartily congratulates Benjamin on his excellent scholastic record and advises him on his future with one word: “Plastics”. Mr. Robinson leaves for the airport, on a business trip, after advising the Braddocks to “pour” his wife into a cab when it’s time for her to go home. Benjamin refuses to join the party, again, declaring the guests to be ”grotesque”, and that his years in school have added up to nothing. His parents exit, annoyed and disturbed.
Benjamin begins to strip off his wetsuit, but is interrupted by Mrs. Robinson, tipsy but controlled, who has come looking for the spare room in which to lie down and rest. To Benjamin’s growing discomfort, she does not leave, and she asks him whether he is upset because of “girl trouble” and if he knew she was an alcoholic. When Benjamin tries to leave the room, Mrs. Robinson asks him to drive her home. Benjamin leaps to a conclusion -- Mrs. Robinson is trying to seduce him -- and is mortified when she replies that she hadn’t thought of it. Benjamin is apologetic, but continues to be uneasy as Mrs. Robinson asks him for a whole list of slightly intimate favors (“unzip my dress?”), culminating in her nudity. Mrs. Robinson tells a horrified Benjamin that she is available to him, any time. Mr. Robinson returns, as there are no flights leaving the airport. Mrs. Robinson retreats to the bedroom, while Benjamin, thoroughly off balance, speaks with Mr. Robinson. Mr. Robinson tells Benjamin that he should sow some wild oats. Mr. Robinson also tells Benjamin that he should call up his daughter, Elaine, for a date -- but emphasizes that she is the kind of girl who must be treated just right.
Mrs. Braddock enters, in time to bid goodbye to the Robinsons. She asks Benjamin when he is coming down to the party. Benjamin responds that he’s leaving town, going on the road. He plans to to work at odd jobs and get in touch with real people -- farmers, truck drivers -- who “don’t have swimming pools.” Mrs. Braddock is distraught but Mr. Braddock, upon entering and hearing about his son’s sudden desire to get out of town, sends him away proudly with some extra cash in his pocket.
An early morning roughly two weeks later, in the same room, a dirty and disheveled Benjamin sits on his bed and endures a cross-examination by his Dad regarding his disappointing road trip, which included a boring fire, some boring farmers, a couple of truckstop whores, and some alcohol. When Mrs. Braddock enters and asks about the trip, Mr. Braddock tries to change the subject, and Benjamin leaves, to take a shower. Mr. Braddock is scornful when his wife says that she thinks Benjamin is disillusioned, like the young people of today she read about in a magazine, but Mrs. Braddock sticks to her opinion.
Benjamin appears in a phone booth, giving Mrs. Robinson a call, to see if she wants to meet for a drink sometime. In return, Mrs. Robinson invites him, immediately, to the Taft Hotel.
In the lobby of the elegant Taft Hotel, Benjamin anxiously approaches the intimidating Desk Clerk, trying to affect a nonchalant demeanor, but embarrassed to actually reserve a room. Mrs. Robinson enters, and calmly takes charge, talking Benjamin firmly through his suggestions that maybe they should get a drink and just talk, and ultimately stepping in when he fumbles his requests to the Desk Clerk. Benjamin gets a single room, but after seeing him in close conference with Mrs. Robinson, the Desk Clerk suggests that maybe a double room would be more suitable, which Mrs. Robinson gracefully accepts, along with the offer of champagne. In the elevator, Benjamin makes nervous conversation, and Mrs. Robinson continues calm and collected.
In Room 515 of the Taft Hotel, Benjamin tells a story about his firefighting adventure, while Mrs. Robinson drinks the champagne, then announces that she is getting undressed. Benjamin tries to kiss her, offers to help her undress, and gets her the wrong type of hanger from the closet. When Mrs. Robinson begins to remover her bra, Benjamin exclaims, “I can’t do this!” and tries to retreat, citing the disappointment his parents would feel if they could see him now. But when Mrs. Robinson gently asks him if it’s his first time, Benjamin bristles at the suggestion that he is in some way “inadequate”, and orders her onto the bed, tearing off his clothes, and falling down in his haste to prove himself.
In one stage locale, Mr. and Mrs. Braddock call into Benjamin’s bedroom, asking him to wake up and do something, anything -- mow the lawn, clean the pool. Simultaneously, in another place, Benjamin and Mrs. Robinson perform various acts of lovemaking, as seen in silhouette from in front of a screen. Time passes.
In Room 515 of the Taft Hotel, Benjamin interrupts their intercourse to ask Mrs. Robinson if they could “just have a conversation.” Mrs. Robinson agrees, but her answers are brief as Benjamin tries to discuss art and tells her about his day, before lighting on the delicate subject of her husband. Benjamin digs deeply, discovering that Mr. and Mrs. Robinson have not slept together in five years, that she never loved him, that she married him because she was pregnant with their daughter Elaine, who happened to be conceived in a car. Benjamin is delighted to hear that “Old Elaine Robinson got started in a Ford.” Mrs. Robinson forbids Benjamin to talk about Elaine, which reminds him -- his parents have been pressuring him to take Elaine out when she comes home from vacation, or else they’d “cut off his allowance, and throw him out of the house.” Mrs. Robinson firmly forbids Benjamin to see Elaine, Benjamin in turn becomes furious, accusing Mrs. Robinson of being jealous that he might like her daughter better, or of thinking that he is too much a “filthy degenerate” to associate with her child. Benjamin is on the verge of walking out when Mrs. Robinson apologizes for giving him the wrong impression, and tells him that she understands why she “might disgust him,” and that their arrangement should come to an end. Benjamin is taken aback, and quickly apologizes in turn, hopping back into bed, and promising never to see Elaine.
Elaine Robinson waits on a darkened Hollywood street corner. Various men mutter lasciviously to her as they pass by, offering her drinks and asking her if she is “looking for business.” Benjamin enters, and leads the way into the Club Renaissance, a fairly tacky bar. Benjamin orders beers for them both, although Elaine says that she never drinks. Elaine asks polite questions, and Benjamin provides abrupt and pessimistic answers. Elaine talks about seeing the Mona Lisa, on loan to the Washington Museum, after attending a civil rights march. A stripper enters, and begins to dance in front of the table. Benjamin tries to get Elaine to watch. Elaine asks Benjamin if he hates her or something. When the stripper musses Elaine’s hair with her pair of swinging tassles, Elaine begins to cry, and Benjamin interrupts the stripper, who retreats to the back room, and he tries to apologize and explain himself to a furious Elaine, telling her that he has been going through a difficult time and that his life is “bullshit.” Elaine tells Benjamin that she feels sorry for him, and complains that she is “always being attached onto by nihilists.” She talks about world events -- war, struggles for justice -- and explains that life is precious. When the stripper returns, Elaine apologizes for interrupting the dance. She and the stripper exchange some friendly words, and Elaine tells Benjamin once more about the silver linings to be found in life. Benjamin kisses Elaine, telling her that her mouth is very “Mona Lisa,” and the two leave to find some dessert.
In the Robinson living room, Benjamin tells Mrs. Robinson that he and Elaine are going for a drive, and Mrs. Robinson tells Benjamin to “turn around and leave the house.” She says that to keep Benjamin away from Elaine, she would say anything she had to. Benjamin asks Mrs. Robinson please not to “wreck it” -- he’s in love. Elaine enters, confused at Benjamin’s early presence and the tension between him and her mother. Benjamin tells Elaine, before Mrs. Robinson can get a chance, about their affair. Horrified, Elaine throws Benjamin out of the house. Elaine takes a bottle of vodka from her mother, pours herself a glass, and starts to drink.
Some hours later, Elaine and Mrs. Robinson are both drunk on vodka. They talk, in confusing fashion, about Benjamin’s horribleness, how to stop the room from spinning, and whether Mrs. Robinson actually loves her daughter, or her husband, or whether any of them love each other. Mrs. Robinson remembers teaching Mr. Robinson how to sing the high notes of songs, after which he never sang again. Elaine declares that she is going to have a forever love, and a skeptical Mrs. Robinson tells her that she can go ahead and try -- as long as it’s not Benjamin.
At the Braddock household, Benjamin is packing his suitcase, telling his Mom and Dad that he is going to marry Elaine Robinson. They are at first elated, and then confused, to hear that not only does Elaine have no idea, she hates Benjamin. Benjamin leaves, planning to move to Berkeley, and propose to Elaine.
In a cramped boarding house room, Elaine confronts Benjamin, asking him what he’s doing in Berkeley, if he moved up there because of her, and why he’s been following her around. Benjamin responds that he loves her, and begs her forgiveness for the things that he’s done. Elaine accuses him of raping her mother, whereupon Benjamin bristles with outrage, and tries to set Elaine straight, replacing the story in which he “drugged Mrs. Robinson and dragged her up to his hotel room” with the truth of his seduction. Elaine does not verbally accept this story, but she ceases her accusations, and questions more closely about his motives and actions, telling him she hopes he has a definite plan before he leaves. Benjamin says that he will leave if she tells him to, but she does not tell him to leave, instead talking about the bartender’s guide that her mother gave her for her eleventh birthday.
As Elaine starts to leave, Benjamin proposes marriage, telling her that he thinks they have “a lot in common.” Elaine admits that she is fond of Benjamin, but tells him that they are too young, that he hasn’t thought about practicalities -- like what kind of cereal to buy -- and lists a number of other objections, all of which he overrules. There is a particular obstacle, however, in Carl Smith, the boy she met last semester, who she thinks she might marry. Benjamin panics at the idea of his medical student rival, asking Elaine numerous questions about the proposal and how it happened, but when Benjamin asks a departing Elaine whether they are getting married, her response is “maybe we are, and maybe we aren’t,” before leaving him with a big kiss, and a grin on his face.
The next day, Benjamin eagerly answers a knock on the door, only to find a disheveled and devastated Mr. Robinson at his doorstep. Mr. Robinson wonders what he has done to Benjamin, why he would want to hurt and disrespect him so much. Benjamin doesn’t make things better by telling Mr. Robinson that it had nothing to do with him. Mr. Robinson reveals that he and Mrs. Robinson are getting a divorce, and Benjamin tells him not to do that -- he loves Mr. Robinson’s daughter, not his wife. Mr. Robinson tells Benjamin that Elaine is going to marry Carl, that if he tries to interfere he will be prosecuted, and that he thinks Benjamin is scum, filth, and totally despicable. He leaves, and a furious Mr. Braddock enters, ready to take Benjamin home, for a morning appointment with a psychiatrist. Benjamin makes a crack about straightjackets, and Mr. Braddock strikes Benjamin across the jaw. Mr. Braddock asks for forgiveness, explaining that he is very badly shaken.
In the psychiatrist’s office, the entire family is talking at once. Mrs. Braddock complains that she doesn’t understand why everything is her fault, just because she’s the mother. She has always given Benjamin everything he wanted, down to smooth or crunchy peanut butter. Mr. Braddock holds forth about the mind of a young man. Benjamin objects to being put in a mental hospital. The psychiatrist says that nothing is anyone’s fault. Mr. and Mrs. Braddock yell at each other. Benjamin, frantic to get away, asks the psychiatrist if he’s insane, and when the psychiatrist says that he doesn’t believe so, Benjamin jumps out the window, as Mrs. Braddock wails that it’s all her fault.
In the vestry of the First Presbyterian Church, Benjamin dashes in, dragging Elaine, in full wedding garb, behind him. He tries various doors, but upon finding that they are broom closets, realizes that he is trapped. Mrs. Robinson slips into the room before Benjamin succeeds in barricading the door against a howling Mr. Robinson, and all the guests who have assembled for Elaine’s wedding to Carl Smith. She tells Elaine to get back into the church. Benjamin insists that Elaine does not want to marry Carl, Mrs. Robinson insists that she does, and Elaine asks them both to stop telling her what to think. She argues with Benjamin about her reasons for marrying Carl. Benjamin insists that she is marrying Carl because she actually loves him, Benjamin, a fact which Elaine cannot confirm or deny. As Elaine wavers, Mrs. Robinson tells her that Benjamin is a depraved character, with a “selfish side so wide it hides his vicious streak,” but falters herself when it comes to pretending that he wasn’t good in bed. Benjamin begs Elaine, then orders her, to take off the wedding dress.
There is a commotion from the door as Mr. Robinson begins to hack his way in with a fire axe. Wedding guests huddle behind him, curious, alarmed, and encouraging, as Mr. Robinson steps through the door and tries to take control, declaring that he is going to cut Benjamin’s “sick head off.” Elaine and Mrs. Robinson talk him into dropping the axe, Elaine reassuring him that “nothing has changed,” and Mr. Robinson shame-facedly asks the priest to send him a bill for the door. The priest and guests exit, as Elaine soothes Mr. Robinson, telling Benjamin that she doesn’t want to “go against the world,” before leaving with her father.
Mrs. Robinson triumphs hollowly over a depressed Benjamin, telling him that he never stood a chance: Elaine can’t make a decision without “crawling into her father’s lap for a few hours,” she’s never wanted anything, she’s conventional, shallow, and dull. Elaine, who has returned for her corsage, overhears this speech, and confronts her mother. After a heated exchange, Elaine asks her mother why she didn’t “go to the clinic and get rid of the baby,” and bursts into tears, Mrs. Robinson steps forward to comfort Elaine, but Benjamin moves forward and faces her down, taking the weeping Elaine into his own arms instead. Mr. Robinson enters and tries to break them up, but Mrs. Robinson tells him to leave them alone, explaining that “Peaches is rebelling,” and telling him furiously to “sing me a song, or speak to my attorney.” Elaine reaches for her mother as the Robinsons exit, but Mrs. Robinson tells Elaine, “marry this conniving son of a bitch, and you’re on your own.” Elaine kisses Benjamin, with defiance.
In a seedy hotel room somewhere in Nevada, at one o’clock in the morning, a just-married Elaine and Benjamin, dazed and exhausted, discuss what sort of breakfast cereal to eat. Elaine asks Benjamin to unzip her dress, in a movement reminiscent of her mother. Once she is undressed, Benjamin’s lack of action makes her lose confidence. She wonders if they have made a mistake, if she should go back to school. Benjamin produces a box of Cheerios, exactly the cereal she was hoping for, and she is delighted. Elaine teaches Benjamin how to eat Cheerios dry, mixing up the different grains for flavor. They sit on the bed, and eat Cheerios.