The show opens during an audition for an upcoming Broadway production. The formidable director Zach and his assistant choreographer Larry put the 24 dancers through their paces. Every dancer is desperate for work ("I Hope I Get It"). After a round of cuts, 17 dancers remain. Zach tells them he is looking for a strong 8-member dancing chorus of four boys and four girls. Wanting to learn more about them, he asks the dancers to introduce themselves. Reluctantly, the dancers reveal their pasts. The stories generally progress chronologically from early life experiences through adulthood to the end of a career.
The first candidate, Mike Costa, explains that he is the youngest of 12 children. He recalls his first experience with dance, watching his sister Rosalie's dance class when he was a preschooler ("I Can Do That"). Mike replaced her one day when she refused to go to class—and he stayed. Bobby Mills tries to hide his unhappy childhood by making jokes. As he speaks, the other dancers distrust this strange audition process and debate what they should reveal to Zach ("And..."), but since they all need the job, the session continues.
Zach is angered that the streetwise Sheila Bryant is seemingly not taking the audition seriously. Opening up, she reveals that her mother married at a young age and her father neither cared about nor loved them. At age six she realized, as had fellow auditionees Bebe Benzenheimer and Maggie Winslow, that ballet helped her escape her unhappy family life ("At the Ballet"). Scatterbrained and tone-deaf Kristine Urich-DeLuca laments being unable to sing, while her husband Al finishes her phrases in tune ("Sing").
Mark Anthony, the youngest dancer, relates his first exposure to the female anatomy and his first wet dream, while the other dancers share their own memories of adolescence ("Hello Twelve, Hello Thirteen, Hello Love"). The 4'10" Connie Wong laments the problems of being short, and Diana Morales recollects her horrible high-school acting class ("Nothing"). Don Kerr remembers his first job at a nightclub and Judy Turner reflects on her problematic childhood while some auditioners talk about their parents' opinions ("Mother"). Greg Gardner discusses discovering his homosexuality and Richie Walters recounts nearly becoming a kindergarten teacher ("Gimme the Ball"). Finally, the newly-buxom Val Clark explains that talent alone isn't everything, and silicone and plastic surgery can really help improve one's image and career prospects ("Dance: Ten; Looks: Three").
The dancers go downstairs to learn a song for the audition's next section, but experienced dancer Cassie Ferguson, who has had notable successes as a soloist, stays onstage to talk to Zach. They have a history together: Zach had previously cast her in a featured part, and they had lived together for several years. Zach tells Cassie that she is too good for the chorus and shouldn't be at this audition. However, she explains her current inability to find solo work and is willing to "come home" to the chorus where she can at least express her passion for dance ("The Music and the Mirror"). Zach relents and sends her downstairs to learn the dance combination.
Zach calls Paul San Marco, who has been reluctant to share his past, on stage for a private talk, and he emotionally relives his childhood and teenage years, his early career in a drag act, facing his manhood and his homosexuality, and his parents ultimately discovering his lifestyle and disowning him for it, before breaking down, with Zach comforting him. Cassie and Zach's complex relationship resurfaces during a run-through of the number created to showcase an unnamed star ("One"). Zach confronts Cassie, feeling that she is "dancing down," and they rehash the issues in their relationship and her career. Zach points to the machine-like movement of the other dancers, who have all blended together and will probably never be recognized individually, and mockingly asks if she wants this. Cassie defiantly defends the dancers: "I'd be proud to be one of them. They're wonderful....They're all special. I'd be happy to be dancing in that line. Yes, I would...and I'll take chorus...if you'll take me."
During a tap sequence, Paul falls and injures his knee that recently underwent surgery. After Paul is carried off to the hospital, all at the audition stand in disbelief, realizing that their careers can also end in an instant. Zach asks the remaining dancers what they will do when they can no longer dance. Led by Diana, they reply that whatever happens, they will be free of regret ("What I Did for Love"). The final eight dancers are selected: Mike, Cassie, Bobby, Judy, Richie, Val, Mark, and Diana.
"One" (reprise/finale) begins with an individual bow for each of the 19 characters, their hodgepodge rehearsal clothes replaced by identical spangled gold costumes. As each dancer joins the group, it is suddenly difficult to distinguish one from the other: ironically, each character who was an individual to the audience seems now to be an anonymous member of a neverending ensemble.