The Stamper's "spoiled," willful, "headstrong," 20s flapper daughter Ginny ("Sister" or Virginia) (Barbara Loden), with bleached hair and makeup, has been something of an embarrassing disappointment for the family - at finishing school, she broke all the rules and was expelled; then at a university, she went "hog wild" and flunked all her courses; finally, in a Chicago art school, she got "tied up with some cake-eater that gets her into trouble just so he can marry her" - but Ace had it annulled by his lawyer. Bud's older sister has returned home a failure for the third time, causing Bud's father to pressure him even more into being a successful flag-bearer for the family. Rebellious, Ginny has gained a bad reputation and has no intention of reforming herself in the backward, rural town:

If you think I'm going to stay here in this god-forsaken town and have people laugh at me and gossip about me, you've got another thing coming, 'cause I'll really give them something to gossip about...I hate it here. I'm a freak in this town. Everybody stares at me on the street like I was something out of a carnival...This is the ugliest place in the whole world. Everywhere you look there's an oil well, even on the front lawn.

Mrs. Stamper's comment about her breakfast-deprived children is rich in emotional meaning: "Neither of my children gets any real nourishment."

In the crowded high school hallway of classmates, both Deanie and Bud walk together hand-in-hand - obviously a radiant Deanie is pleased to be admired and possessed by the school's handsome football hero. Chivalrously, he accompanies her to her English class and carries her textbooks for her. She is tardy to her seat and reprimanded by her prim, bespectacled teacher Miss Metcalf (Martine Bartlett). [A student is writing on the chalkboard "still unravished."] Oblivious as her teacher lectures about literature of the Middle Ages and stories of King Arthur and the Knights of the Round Table, Deanie doodles in her notebook, scrawling various versions of "Mrs. Arthur Stamper" and "Bud & Deanie." Girlfriends June (Marla Adams), Carolyn (Lynn Loring), and Kay (Sandy Dennis in her first film appearance) whisper about Bud and who's taking whom to the football game:

Kay: Just because his father's got money...
Carolyn: That's not true, Kay...
June: Bud Stamper isn't stuck on himself at all.

A flapper-styled, not-so-innocent, slutty Juanita Howard (Jan Norris) answers the teacher's question about a characteristic of the Age of Chivalry: "The Knights of the Round Table had a very high regard for women...They looked on women as very pure." Kay snidely utters an aside: "They wouldn't look on her as very pure." Deanie appears dreamy-eyed when Miss Metcalf rhetorically asks whether chivalry is dead: "Well, how about it, girls? Do any of you feel that you are on a pedestal?"

During the school's football game, Bud is thrown out by the referee for unsportsmanlike conduct. In the shower room after the game, Bud (with his face under a steady shower stream) overhears his teammates joke with Alan Tuttle ("Toots") (Gary Lockwood) about taking out the sexually-experienced Juanita. According to him, "Juanita's the only girl in school who knows what it's all about...I never look twice at those other girls anymore. Ya take them out and spend good money on 'em, and they expect you to feel satisfied if they even kiss you good night."

Outside the school gym, Deanie jealously reprimands Bud after he flirts with red-headed Juanita on his way to the car - and he is furious: "I'm not even supposed to know girls like that exist, huh?" When they reach her house, she is still repeatedly apologizing for her possessiveness and they affectionately make up:

Deanie: (with her head on his shoulder) I just can't stand it when you're mad at me...
Bud: I don't know what's the matter with me lately. I'm always losing my temper. You're the only girl in the world for me. Don't you know that, Deanie?
Deanie: I want to be.
Bud: If it weren't for you...if it weren't for you, Deanie - I don't know. (He smashes a fist into his hand)
Deanie: (She caresses his cheek gently and kisses him. He kisses her back and pulls her toward him.) Oh, Bud, Bud, it's broad daylight. Stop it. Stop it. Come on now. Bud! People can see us.
Bud: I don't care!

They enter the empty house and check to insure their privacy in the parlor. Being head-over-heels in love with him, Deanie begins to show her sacrificial devotion after he has shown interest in someone else. She peppers him with kisses all over his face - and then when they hear voices, they retreat into the side dining room. Through a framed doorway, the camera eavesdrops on their overheated love scene. Deanie presses her groin into his as they lean against a door. Bud forcefully grabs her shoulders and presses her down to her knees to make her confess her utter obedience to his will:

Bud: You're nuts about me, aren't you? You're nuts about me....(After making out a while, he begins to touch her below the waist.)
Deanie: No, Bud...
Bud: (He pushes her down to her knees in front of him.) At my feet, slave!
Deanie: Bud, don't.
Bud: Tell me you love me.
Deanie: Bud, you're hurting me.
Bud: Tell me you can't live without me. Say it.
Deanie: I do.
Bud: You do what?
Deanie: I do love you.
Bud: And you can't live without me...And you'd be everything I ever ask you to be, anything.
Deanie: (fearfully) I-I'd do anything for you.
Bud: Deanie, I didn't mean to hurt you. (She lies on the floor, curled up protectively.) Deanie, Deanie! Deanie, I was just kidding. Look, I'm the one who should go down on my knees to you, Deanie. Deanie, I was just kidding. I thought you knew that.
Deanie: (sincerely) I can't kid about these things. Because I am nuts about you, and I would go down on my knees to worship you if you really wanted me to. Bud, I can't get along without you. And I would do anything you'd ask me to. I would! I would! Anything!

After her confession of complete submission, she rolls over onto her back in a sublime, vulnerable state of passionate surrender, moaning orgasmically and begging for "anything" to happen: "Oh Bud. - Bud! - Bud." When they hear the intrusive Mrs. Loomis returning to the house, Deanie hurriedly straightens herself and they begin playing a regimented duet of Chopsticks on the piano. With lines dripping with sexual innuendo, Deanie is prepared to give into her passions now that Bud has increased his sexual demands and they can't ignore their emotions - the two make plans for an eventful evening:

Deanie: Are we going to the Victory Dance?
Bud: I can think of things I'd rather do.
Deanie: (after warily looking around) I'll be ready.

Once Bud has left and promised to return to pick her up for the dance after dinner, Deanie learns from her mother that Bud's sister Ginny has a bad reputation. She was put "in the family way" by a man in Chicago and had to be taken to a doctor for an abortion - "one of those awful operations." The shrewish Mrs. Loomis strikes fear in her daughter about falling in love: "That's what happens to girls who go wild and boy crazy."

Upon his return home, Bud announces personal decisions to his manipulative father about his career plans, asserting: "It's what I want that counts." His true wishes are to marry Deanie and attend an agricultural college:

Dad, I'm gonna marry Deanie...I don't really want to go to Yale. I'm not a very good student...I'd like to go away to a good agricultural college for a couple of years. I'd really like to do that, Dad. I could come right back here and I could take over your ranch just south of town...I could marry Deanie. I could take her off to college with me. That's what I really want. She'd be a big help to me, Dad.

Mr. Stamper ignores his son's deepest goals, and attempts to convince him to wait about marriage. But Bud, sexually frustrated and unable to postpone his pent-up desires any longer, clenches his teeth in protest. He is advised that there are "two kinds of girls" - and the 'loose' ones are available to sow some wild oats ("get a little steam outa our system"). Adding to the complexity of Bud's confusion is that he feels sexual passion for Deanie - one of the 'good' girls. After realizing he's beaten by his dominating father's hypocritical, morally-corrupt bargain, Bud doesn't follow his own heart - he agrees to go to Yale for four years before marriage:

Mr. Stamper: Son, a boy your age doesn't even know what he wants. After you've had a college education, then you might change your mind...Trust me, trust me this time, son....(rising and moving forward) Son, all I'm asking you to do is to finish Yale. And then if you still want to marry the li'l Loomis girl, you come back here and you marry her, boy, with my blessing. I'll send you both off to Europe for a honeymoon. Bud, please wait, son!
Bud: I just don't know if I can, Dad! I feel like I'm going nuts sometimes.
Mr. Stamper: I understand. (He places his arm over his boy's shoulder.) Your old man understands. What you need for the time being, Bud, is a different kind of girl. When I was a boy, son, there was always two kinds of girls. Us boys - we-we'd never even mention them in the same breath. But every now and then, one of us boys'd sneak off with a girl - and we'd get a little steam outa our system.
Bud: Dad, Dad, no girl looks good to me except Deanie.
Mr. Stamper: I know.
Bud: I love her, Dad!
Mr. Stamper: I know, son, I know!
Bud: See, I don't want to do that. (agonizing) OK. I'll go to Yale. But I want you to know that I'm gonna marry her as soon as I get out.
Mr. Stamper: That's a promise.
Bud: I want you to remember that.

Rain streaks down the windshield of Bud's sportster parked by the waterfall - the couple's faces are blurred by the glass as she vows to be faithful for four long years:

Bud, I'll wait for you. I'll wait for you forever. I'll do anything you want, Bud.

In the Sunday church service, Reverend Whiteman (uncredited screenwriter William Inge himself) sermonizes: "Lay not up treasures for yourself on earth. Where moth and rust doth corrupt and where thieves do break through and steal. But lay up for yourself treasures in heaven where neither moth nor rust doth corrupt and where thieves do not break through and steal. Where your treasure is, there will your heart be also." Deanie lovingly reaches for Bud seated next to her, while Mr. Stamper, the one most in need of heeding the Biblical words, snoozes. After the service, Bud's father requests that his son "spy" ("keep an eye") on Ginny while he's away on a short trip to New York: "She won't do anything crazy when you're around."

At the Stamper's dinner table that evening, Bud's sister has attracted a muscular, ignorant boyfriend named Glenn (Sean Garrison). With his unemployed father, he is a newcomer to town from Oklahoma and works in the local filling station. Deanie is both amused and repelled by Ginny's sassiness (termed a "bad nature" by her mother). When they double-date together after dinner at one of the outlying ranch properties on the sprawling Stamper estate, Ginny taunts her do-good, miserable, and sexually-repressed brother:

Why don't you quit trying to pretend you're so pure and righteous...You never do anything except what Dad tells you - isn't that right, Deanie? You've been finding that out, haven't you? He just lets things torment him inside and make him miserable and he never does anything about them, never does anything.

Deanie and Bud gaze out over a landscape dotted with creaking oil wells - Bud assures his fiancee: "All this - it's gonna be ours some day."

Later, on Christmas day, Ginny cautions her stunned brother after slapping him. She challenges him to confront their father: "If you want to listen to Dad, go ahead. One of these days, you'll find out. You'll find out and then God help you."

At a New Year's Eve country-club dance to bring in 1929, Ginny lives up to her reputation as a booze-drinking, loose trollop - dipping and passing out gin drinks from a huge bathtub to a horde of male admirers. During the countdown to the next year, Mr. Stamper pops with a lit cigar an inflated pink balloon (with "'28" imprinted on it) atop a model of one of his golden oil derricks. The sexually-suggestive symbolism (of wealth and male power) is further amplified when a stream of champagne shoots up from the top of the oil rig - while the band plays "Auld Lang Syne." He is assured of prosperity in the coming year, but repelled by the spectacle of his drunken, uninhibited daughter kissing him in public: "You cut that out. You behave yourself." Shattered by her father's curt rejection but remaining defiant, Ginny turns to heavy drinking, soon becomes inebriated ("plastered"), and flirtatiously flaunts her wantonness in front of married men. She barges into the Men's Room - and amidst protests, emerges guzzling from an upturned whiskey flask.

Mr. Stamper instructs Bud to take the soused woman home, and Bud dutifully leads her away from the party onto the porch. A group of her former partners witness her outspokenness toward her upset brother:

If you weren't my brother...you wouldn't even come near me...You're a nice boy. You're nice. I know what you nice boys are like. I know - you only talk to me in the dark. IN THE DARK!

When she pulls away from him and is left with at least eight 'nice-looking' boys on the porch, they paw at her and kiss her. After she implores one of them (Joe) to take her "anywhere!!!," she is led into the dark parking lot and trailed by the men - and a gang-rape is implied within one of the sedans. As Bud seeks to rescue and defend her, he finds the waist-sash from her dress on the ground. He angrily drags Joe from the car and fights him and others off in a bloody melee, as Ginny starts the car and tries to run them over as she drives off.

Unaware of the reason for the fight, Deanie searches for Bud in the parking lot. With a bloody lip and bruised face, he staggers and falls into her arms. After driving her home, he withdraws within himself and refuses her comforting invitation to come inside. With increased torment in his own mind, he decides to break off their relationship for a while and stop seeing her:

We've got to stop all this kissing and foolin' around, Deanie...I just don't think we'd better see each other for a while.

Deanie stands on the curb - puzzled, frozen and stunned by his sudden decision.

After some time has passed, Bud is in school's basketball practice - preoccupied, bewildered, exhausted, and unable to concentrate. In his English class, Bud is equally dazed when he receives a "not very good" grade on his term paper from his teacher, Miss Longfield: "You've got to do much better if you're going to get into Yale in the fall." In the hallway, Deanie is expectantly waiting for him: "I miss you, Bud." During a basketball game as he completes a lay-up, Bud bumps into a padded pole and soon falls down unconscious. The Stampers' family doctor Doc Smiley (John McGovern) attends to feverish Bud in the locker room and recommends hospitalizing him - he may have pneumonia. In the hallway of the hospital with Deanie listening intently from a short distance away, the doctor speaks with Mr. Stamper and wonders if Bud will recover: "I'm not a religious man, but I know what every doctor knows - you can't...reckon with the will of God."

That night, Deanie prays with Reverend Whiteman to heal Bud: "All I can think of is, 'Dear God, make him well, make him well.'" Agonizing over her ex-boyfriend's health, Deanie kneels in the pew: "Oh, please God, make him well. Make him well." Sometime later, in Doc Smiley's office, Bud is recovering his strength - and receiving a sunlamp treatment. When he turns to the unhelpful doctor for advice about his relationship with the "mighty attractive" Deanie, Bud describes the painful toll it has taken on him, and his father's suggestion to find a girl who is more accommodating:

I'm pretty nuts about Deanie Loomis...I mean I love her and she loves me. But it's no fun to be in love. It hurts. Every time that we're together, I have to remember things - you know what I mean?...And I can't just go back to seeing her again, not like the way we were doing. We'd go out every night and I'd kiss her - I'd just go home. I mean, a guy can go nuts that way...My dad said that I should get another kind of a girl...but when you don't really want another girl...I don't know.

It is late springtime and from a long shot, Bud and Juanita bask in the hot afternoon sun on the rocks in front of the waterfall. Unable to restrain his sexual needs, he has chosen to have a tryst with the most promiscuous girl in the school. In contrast to his date with Deanie at a distance from the falls in the film's opening, he is now at the foot of the falls with Juanita. She rubs his bare chest and kisses it, whispers into his ear - and then they playfully cavort in their underwear under the falls. She giggles as they lovingly embrace, with soaked and clinging undergarments, within the roar of the gushing water.

In the school corridor - now without Bud and knowing that he is dating Juanita, a lonely and melancholy Deanie walks alone to her English class, disengaged and out of synchronization with her surroundings. Miss Metcalf recites from William Wordsworth's 1807 poem:

What though the radiance which was once so bright
Be now forever taken from my sight,
Though nothing can bring back the hour
Of splendor in the grass, of glory in the flower,
We will grieve not, rather find
Strength in what remains behind

She then calls on an inattentive Deanie to interpret its meaning in front of the class. Deanie rises and reads the phrases aloud from her textbook, with tears welling up in her eyes and an uncomfortable lump in her throat, and then she interprets the lines with great difficulty - with Juanita looking up from the seat in front of her. She strains not to reveal the pain in her heart, suddenly realizing that her relationship with Bud may be over, and that her youthful ideals must give way to adulthood:

Well, I think it has some...Well, when we're young, we look at things very idealistically, I guess, and I think Wordsworth means that when we grow up, that we have to forget the ideals of youth and find strength...

Normally, Deanie wouldn't take the poetry that is being taught by her high school teacher very seriously. But explaining a poem about the termination of an eternal love affair is just too much for her. Devastated and overcome, she slowly walks to the front of the room with her textbook still cradled in her arms and her hand shielding and cradling the side of her face - to ask to be excused. Experiencing a nervous breakdown, she runs from the classroom before finishing her sentence. Upset, Juanita begins crying. In the school nurse's office, Deanie denies that she has a problem - she both giggles and cries hysterically: "I'm all right, I'm perfectly all right." In a darkened movie theatre, a brooding Bud and two buddies discuss Deanie. When Toots asks about dating Bud's ex-girlfriend ("Hot dog - now it's my chance"), Bud apathetically doesn't object: "I can't stop you."

Deanie's subsequent, heart-breaking mental and emotional breakdown, due to acquiescence to her parents, is shown in stages. In her home, her father and mother propose that a full-course, nourishing midwestern meal smothered with gravy will make her feel better: "Veal roast, mashed potatoes, and succotash for my girl. Eat a good meal, Deanie. Make you feel better. Always drink plenty of milk, Deanie." She trembles and jumps up from the table when her father mentions Bud's acquisition of a brand new car because the Stamper oil industry is thriving and making everyone rich. Spiraling downward, she has suicidally lost all will to live:

Mom, I can't eat, I can't study. I can't even face my friends anymore. I want to die. I want to die.