On the soon-to-be demolished stage of the Weismann Theatre, a reunion is being held to honor the Weismann's "Follies" shows past, and the beautiful chorus girls who performed there every year between the two world wars. The once resplendent theatre is now little but planks and scaffolding. As the ghosts of the young showgirls slowly drift through the theatre, a majordomo enters with his entourage of waiters and waitresses. They pass through the spectral showgirls without seeing them.
Sally Durant Plummer, "blond, petite, sweet-faced" and at 49 "still remarkably like the girl she was thirty years ago", a former Weismann girl is the first guest to arrive; her ghostly youthful counterpart moves towards her. Phyllis Rogers Stone, a stylish and elegant woman, also arrives with her husband Ben, a renowned philanthropist and politician. As their younger counterparts approach them, Phyllis comments to Ben about their past. He feigns disinterest; there is an underlying tension in their relationship. As more guests arrive, Sally’s husband, Buddy, enters. He is a salesman, in his early 50s, appealing and lively, whose smiles cover inner disappointment.
Finally, Weismann enters to greet his guests. Roscoe, the old master of ceremonies, introduces the former showgirls. Former Weismann performers at the reunion include Max and Stella Deems, who lost their radio jobs and became store owners in Miami; Solange La Fitte, a coquette, who is vibrant and flirtatious even at 66; Hattie Walker, who has outlived five younger husbands; Vincent and Vanessa, former dancers who now own an Arthur Murray franchise; Heidi Schiller, for whom Franz Lehár once wrote a waltz; and Carlotta Campion, a film star who has embraced life and benefited from every experience.
As the guests reminisce, the stories of Ben, Phyllis, Buddy and Sally unfold. Phyllis and Sally were roommates while in the Follies, and Ben and Buddy were best friends at school in New York. When Sally sees Ben, her former lover, she greets him self-consciously. Buddy and Phyllis join their spouses and the foursome reminisces about the old days of their courtship and the theatre, their memories vividly coming to life in the apparitions of their young counterparts. Each of the four is shaken at the realization of how life has changed them. Elsewhere, Willy Wheeler (portly, in his sixties) cartwheels for a photographer. Emily and Theodore Whitman, ex-vaudevillians in their seventies, perform an old routine. Solange proves she is still fashionable at what she claims is 66, and Hattie Walker performs her old showstopping number.
Buddy warns Phyllis that Sally is still in love with Ben, and she is shaken by how the past threatens to repeat itself. Sally is awed by Ben’s apparently glamorous life, but Ben wonders if he made the right choices and considers how things might have been. Sally tells Ben how her days have been spent with Buddy, trying to convince him (and herself). But it is clear that Sally is still in love with Ben – even though their affair ended badly when Ben decided to marry Phyllis. She shakes loose from the memory and begins to dance with Ben, who is touched by the memory of the Sally he once cast aside.
Phyllis interrupts this tender moment and has a biting encounter with Sally. Before she has a chance to really let loose, they are both called on to participate in another performance – Stella Deems and the ex-chorines line up to perform an old number, as they are mirrored by their younger selves. Afterward, Phyllis and Ben angrily discuss their lives and relationship, which has become numb and emotionless. Sally is bitter and has never been happy with Buddy, although he has always adored her. She accuses him of having affairs while he is on the road, and he admits he has a steady girlfriend, Margie, in another town, but always returns home. Carlotta amuses a throng of admirers with a tale of how her dramatic solo was cut from the Follies because the audience found it humorous, transforming it as she sings it into a toast to her own hard-won survival.
Ben confides to Sally that his life is empty. She yearns for him to hold her, but young Sally slips between them and the three move together. Ben, caught in the passion of memories, kisses Sally as Buddy watches from the shadows. Sally thinks this is a sign that the two will finally get married, and Ben is about to protest until Sally interrupts him with a kiss and runs off to gather her things, thinking that the two will leave together. Buddy leaves the shadows furious, and fantasizes about the girl he should have married, Margie, who loves him and makes him feel like "a somebody", but bitterly concludes he does not love her back. He tells Sally that he's done, but she is lost in a fantasy world, and tells him that Ben has asked her to marry him. Buddy tells her she must be either crazy or drunk, but he's already supported Sally through rehab clinics and mental hospitals and cannot take any more. Ben drunkenly propositions Carlotta, with whom he once had a fling, but she has a young lover and coolly turns him down. Heidi Schiller, joined by her younger counterpart, performs "One More Kiss", her aged voice a stark contrast to the sparkling coloratura of her younger self. Phyllis kisses a waiter and confesses to him that she had always wanted a son. She then tells Ben that their marriage can't continue the way it has been. Ben replies by saying that he wants a divorce, and Phyllis assumes the request is due to his love for Sally. Ben denies this, but still wants Phyllis out. Angry and hurt, Phyllis considers whether to grant his request.
Phyllis begins wondering at her younger self, who worked so hard to become the socialite that Ben needed. Ben yells at his younger self for not appreciating all the work that Phyllis did. Both Buddys enter to confront the Bens about how they stole Sally. Sally and her younger self enter and Ben firmly tells Sally that he never loved her. All the voices begin speaking and yelling at each other. Suddenly, at the peak of madness and confusion, the couples are engulfed by their follies, which transform the rundown theatre into a fantastical "Loveland", an extravaganza even more grand and opulent than the gaudiest Weismann confection: the place where lovers are always young and beautiful, and everyone lives only for love. Sally, Phyllis, Ben and Buddy show their "real and emotional lives" in a sort of group nervous breakdown.
What follows is a series of musical numbers performed by the principal characters, each exploring their biggest desires. The two younger couples sing in counterpoint of their hopes for the future. Buddy then appears and performs a high-energy vaudeville routine depicting how he is caught between his love for Sally and Margie's love for him. Sally appears next, singing of her passion for Ben from the past- and her obsession with him now. In a jazzy dance number, accompanied by a squadron of chorus boys, Phyllis reflects on the two sides of her personality, one naive and passionate and the other jaded and sophisticated and her desire to combine them. Ben begins to offer his devil-may-care philosophy, but stumbles and anxiously calls to the conductor for the lyrics, as he frantically tries to keep going. Ben becomes frenzied, while the dancing ensemble continues as if nothing was wrong. Amidst a deafening discord, Ben screams at all the figures from his past and collapses as he cries out for Phyllis.
"Loveland" has dissolved back into the reality of the crumbling and half-demolished theatre; dawn is approaching. Ben admits to Phyllis his admiration for her, and Phyllis shushes him and helps Ben regain his dignity before they leave. After exiting, Buddy escorts the emotionally devastated Sally back to their hotel with the promise to work things out later. Their ghostly younger selves appear, watching them go. The younger Ben and Buddy softly call to their "girls upstairs", and the Follies end.
