Plot

Austria, circa 1900: the actress Desiree Armfeldt becomes entangled with multiple intersecting love affairs, which all converge for an evening at the Viennese country estate of her mother, a former courtesan.

Frederick Egerman (Len Cariou) appears happily married to seventeen-year-old Anne (Lesley-Anne Down), only she's remained a virgin for all eleven months of the marriage. Being a bit restless, Fredrick goes to see an old flame, the celebrated actress Desiree Armfeldt (Dame Elizabeth Taylor). Growing tired of her "Glamorous Life" on the road, Desiree considers settling down, setting her sights on Fredrick, despite his marriage, and her own established affair with Count Carl-Magnus Mittelheim (Laurence Guittard). Desiree gets her mother to invite the Egermans to her country estate for the weekend. But when Carl-Magnus and his wife Charlotte (Dame Diana Rigg) appear, too, things begin to get farcical ("Send in the Clowns"), and the night must smile for three times before all the lovers are united.—Kathy Li

Set in Vienna, Austria in the year 1900, the film opens with a staged musical number by the Quintet. Their vocalizing becomes an overture blending fragments of "Remember," "Soon," and "The Glamorous Life," leading into the first "Night Waltz". The other characters enter waltzing, each uncomfortable with their particular partner.

As the stage fades away, the opening exterior scene shows the aging and severe Madame Armfeldt (Hermione Gingold) and her solemn 15-year-old granddaughter, Fredericka Armfeldt (Chloe Franks). Madame Armfeldt tells the child that the summer night "smiles" three times: first on the young, second on fools, and third on the old. Fredericka vows to watch the smiles occur.

Frederick Egerman (Len Cariou) is a middle-aged successful lawyer. He has recently married an 18-year-old trophy wife, Anne (Lesley-Anne Down), a vain girl who is in love with Frederick, but too immature to grasp the concept of marriage. The two have been married for eleven months, but Anne still protects her virginity. Frederick laments his inability to make love to his wife ("Now").

Meanwhile, Frederick's son Erich (Christopher Guard), a year older than his stepmother, is feeling extremely frustrated. He is a seminary student and everyone is always teasing him, never taking him seriously or letting him talk ("Later"). Anne is intrigued by him, but fails to understand his real meaning. Anne promises her husband that she will consent to have sex shortly ("Soon"). Anne's maidservant Petra (Lesley Dunlop), an experienced and forthright girl, slightly older than the teen herself, offers her worldly but crass advice.

Elsewhere, Desiree Armfeldt (Elizabeth Taylor) is a prominent and glamorous actress who is now reduced to touring in small towns. Madame Armfeldt, Desiree's mother, has taken over the care of Desiree's daughter Fredericka. Fredericka misses her mother, but Desiree continually puts off going to see her, preferring, somewhat ironically, "The Glamorous Life". She is performing near Frederick's home, and he brings Anne to see the play. While there, Desiree notices Frederick; the two were lovers years before. Anne, suspicious and annoyed because of Desiree's amorous glances, demands that Frederick bring her home immediately. Meanwhile, Petra has been trying to seduce Erich.

That night, as Frederick remembers his past with Desiree, he sneaks out to see her; the two share a happy but strained reunion, as they "Remember". They reflect on their new lives, and Frederick tries to explain how much he loves Anne ("You Must Meet My Wife"). Desiree responds sarcastically, boasting of her own adultery, as she has been seeing the married dragoon, Count Carl-Magnus Mittelheim (Laurence Guittard). Upon learning that Frederick has gone for eleven months without sex, she agrees to accommodate him as a favor for an old friend.

At the country house, Madame Armfeldt offers advice to young Fredricka. The elderly woman reflects poignantly on her own checkered past, and wonders what happened to her refined "Liaisons".

Back in Desiree's apartment, Count Carl-Magnus Mittelheim pays an unannounced arrival in his typical booming voice. Frederick and Desiree fool the gullible Count into believing that their disheveled appearance was entirely innocent as Frederick is washing his clothes in the wash, but the Count is still suspicious. He instantly dislikes Frederick and returns to his wife, Countess Charlotte (Diana Rigg). Charlotte is quite aware of her husband's infidelity, but Carl-Magnus is too absorbed in his suspicions of Desiree to talk to her ("In Praise of Women"). When she persuades him to blurt out the whole story, a twist is revealed: Charlotte's little sister is a school friend of Anne's.

Charlotte visits Anne, who is talking with Petra. Charlotte describes Frederick's meeting with Desiree; Anne reacts with shock and horror. The older woman explains to Anne that such is the lot of a wife, and that marriage brings pain ("Every Day A Little Death"). Meanwhile, Desiree asks Madame Armfeldt to host a party for Frederick, Anne, and Henrik. Though reluctant, Madame Armfeldt agrees. She sends out a personal invitation; its receipt sends the women into a frenzy ("A Weekend in the Country"). Anne does not want to accept the invitation, but Charlotte convinces her to do so to heighten the contrast between the older woman and the young teenager.

Meanwhile, the Count has plans of his own as a birthday present to his wife, the pair will attend the party uninvited. Carl-Magnus plans to challenge Frederick to a duel, while Charlotte hopes to seduce the lawyer to make her husband jealous and end his philandering. The day of the party dawns.

Armfeldt's country estate is bathed in the golden glow of perpetual summer sunset at this high latitude ("Night Waltz One and Two"). Everyone arrives, each carrying their own amorous purposes and desires; even Petra, who catches the eye of Armfeldt's fetching manservant, Frid. The women begin to act against each other. Frederick is astonished to learn the name of Desiree's daughter. Erich meets Fredericka, and confesses his deep love for Anne to her.

Meanwhile, in the garden, Frederick and Carl-Magnus reflect on how difficult it is to be annoyed with Desiree, agreeing "It Would Have Been Wonderful" had she not been quite so wonderful. Dinner is served, and the characters' "Perpetual Anticipation" enlivens that meal.

At dinner, Charlotte attempts to flirt with Frederick, while Anne and Desiree trade insults. Soon, everyone is shouting and scolding everyone else, except for Erich, who finally stands up for himself. He shrieks at them for being completely amoral, and flees the scene. Stunned, everyone reflects on the situation and wanders away. Fredericka tells Anne of Erich's secret love, and the two dash off searching for him.

Meanwhile, Desiree meets Frederick in his room and asks if he still wants to be "rescued" from his life. Frederick answers honestly that he loves Desiree, but only as a dream. Hurt and bitter, Desiree can only reflect on the nature of her life ("Send in the Clowns").

Outside, Anne finds Erich, who is attempting to commit suicide. The clumsy boy cannot complete the task, and Anne tells him that she has feelings for him, too. The pair begins to kiss, which leads to Anne's first sexual encounter.

Not far away, Frid sleeps in Petra's lap. The maid thinks of the joy and freedom that she longs for before becoming trapped in marriage ("The Miller's Son").

Erich and Anne, happy together, run away to start their new life. However, Carl-Magnus is enraged by this and attempts to shoot the lovers, but Desiree and Charlotte prevent him, while lamenting both the pains of marriage and the strange behavior of married people ("The World Won't End/Every Day a Little Death (reprise)"). Carl-Magnus calmed, Charlotte confesses her plan to Frederick, and the two commiserate on a bench. Carl-Magnus, preparing to romance Desiree, sees this and challenges Frederick to Russian Roulette, at which a nervous Frederick misfires and simply grazes his own ear. Victorious, Carl-Magnus begins to romance Charlotte, granting her wish at last.

After the Count and Countess leave, Fredericka and Madame Armfeldt discuss the chaos of the recent turns-of-events. The elderly woman then asks Fredrika a surprising question: "What is it all for?" Fredrika thinks about this, and decides that it "must be worth it". Madame Armfeldt is surprised, ruefully noting that she rejected love for material wealth at Fredrika's age. She praises her granddaughter and remembers true love's fleeting nature.

Frederick finally confesses his love for Desiree, acknowledges that Fredrika is his daughter, and the two promise to start a new life together ("Finale"). Armfeldt sits alone with Fredrika. Fredericka tells her grandmother that she has watched carefully, but still has not seen the night smile. Armfeldt laughs and points out that the night has indeed smiled twice: Erich and Anne, the young, and Desiree and Frederick, the fools.

The whole cast then ends the film in the same stage setting which book-ends the film with all the happy couples, Erich and Anne, Count Carl and Charlotte, Frederick and Desiree, as well as the old Madame Armfeldt sitting alone and the girl Fredericka singing solo of the "night music" and what life has to offer.