Act I

The show opens in 1927 outside Graumann's Chinese Theatre on Hollywood Boulevard at the opening night of Don Lockwood and Lina Lamont's new movie, a silent swashbuckler, The Royal Rascal. Fans press forward eagerly as Don gives gossip columnist Dora Baily a highly fictionalized account of his early life. The audience is let into the secret of the real rise of Lockwood from vaudeville to movie star (Fit as a Fiddle).

The film The Royal Rascal is a wild success. It is after the movie's premiere that we learn why Don would not let his leading lady make a speech to the movie theatre audience - Lina has a voice to shatter glass.

Eager to escape from Lina, who is beginning to believe the studio publicity department's story of the romance between them, Don sends his friend and ex-dancing partner Cosmo Brown to the studio party with Lina. Don goes for a walk and to escape from fans, he pretends to be with a girl who is sitting on a bench. The girl, Kathy Selden, wants to be a serious actress and is wholly unimpressed by the screen idol that is Don Lockwood (You Stepped Out of a Dream).

Later at his party (Temptation), studio boss R.F. Simpson gives a demonstration of the new talking pictures. R.F. presents the guests with a giant cake, out of which pops Kathy who, much to her embarrassment, comes face to face with none other than Don Lockwood (All I Do). Don immediately makes fun of the fact that having claimed to be a serious actress, she is working as a dancer. Kathy throws a pie at him, misses and hits Lina instead (You Stepped Out of a Dream reprise). Don is smitten!

On stage at Monumental Pictures, Don is getting ready to shoot his new movie. All the while he is brooding about Kathy. Cosmo tries to cheer him up (Make 'em Laugh). The director of the movie, the larger-than-life Rosco Dexter, arrives to begin shooting The Duelling Cavlier. Don and Lina begin their love scene but when Don discovers that Lina got Kathy fired, the love scene degenerates into a row. Then R.F. closes the production down - he has decided to shoot the movie as a talkie!

Kathy gets a job in Monumental's first musical (Beautiful Girl). Spotted in the chorus, she sings for R.F. and Cosmo, who has been appointed head of the musical department. Don hear her, too. Kathy is put under contract (Lucky Star) on condition that the news is kept from Lina. It is on the now-deserted sound stage that Don declares his love for Kathy (You Were Meant for Me).

Preparing for their first talkie, Don and Lina are having elocution lessons. Lina's is going badly, but Don is doing well, although Cosmo arrives to mock them (Moses Supposes).

Filming of The Duelling Cavalier hits problems as the sound men desperately try to find a place for the microphone. "It's in the bush," Rosco tells Lina - again and again - but she is hopeless (Moses Supposes reprise). The preview of the movie is a disaster: the dialogue is trite, Lina's voice is awful and so is the sound quality. The audience is appalled. The studio faces ruin if the film's problems cannot be fixed.

Don is depressed, until Kathy and Cosmo come up with the solution - why not remake the picture as a musical with Kathy dubbing Lina's voice? (Good Morning). The trio celebrate this brilliant idea. Don walks home on air - in the rain! (Singin' in the Rain).

Act II

The picture is nearly completed, but R.F. wants a production number. Cosmo suggests a flash forward and the number comes to life (Broadway Melody). Kathy is recording Lina's singing and dialogue at night so that Lina won't find out (Would You - Lina; Would You - Kathy). But Zelda has told Lina what is going on, and she bursts in to catch Don and Kathy kissing. Furious, Lina threatens revenge (What's Wrong with Me?).

The opening of the renamed film, The Dancing Cavalier, is a success. Lina insists that Kathy be kept only for her voice and be given no career of her own. Even R.F. has had enough, and when Lina insists on making a speech, he doesn't try to stop her (Lucky Star reprise). The audience is shocked to hear her real voice - they demand a song. Kathy sings behind a screen while Lina mimes a reprise of the show's hit song. Don and Cosmo move the screen to reveal Kathy singing. The audience is hysterical and Lina is humiliated. Kathy runs from the stage, but Don stops her. She is now the real star - not Lina. Kathy's career is now assured and she and Don embrace (You are My Lucky Star reprise) (Singin' in the Rain).