Act One

The action begins on a Friday night in Saigon in April 1975. Backstage at Dreamland, an after-hours club that is frequented by American Marines, a group of bar girls are preparing for their performance. The Engineer, who owns the club, introduces them to a new girl, Kim. She is a 17-year-old orphan who has fled the countryside after seeing her family destroyed ("Opening Act I"). Afraid that the enemy forces of the Vietcong will kill them if they are left behind when Saigon falls, the bar girls are eager to connect with an American G.I. who can get them out of the country. The Engineer also wants to get his hands on a visa, so that he can escape when the Americans pull out. He sends the girls onstage for a sham beauty contest to select a "Miss Saigon."

Next, a group of Marines enters the bar; among them are two friends, Chris and John. Although Chris is reluctant, John insists that a night at the club is what they need to escape the increasing sense of danger from the approaching enemy ("The Heat Is on in Saigon"). When the Engineer thrusts her forward to solicit the crowd, Chris is astounded by Kim's innocence. Meanwhile, one of the girls, Gigi, is crowned Miss Saigon and promptly auctioned off to a G.I. When she asks him if he will marry her and take her to America, however, he leaves. As a result, Kim is brutally punished by the Engineer. Gigi and the other girls dream of leaving this life and finding something better ("The Movie in My Mind"). Sensing that Chris is interested in Kim, John bargains with the Engineer to secure her for his friend ("Bartering for Kim"). Kim and Chris dance, and Chris remarks on how she shouldn't be in a place like this. She leads him away to her room ("Kim & Chris Dance").

Chris, deeply touched by what he has shared with Kim, quietly leaves the room while she is sleeping. Walking through the street, he questions why he has had this profound experience just as he is about to leave Saigon. He is drawn back to the room ("Why God, Why?"). He tries to give Kim money, but Kim refuses to take it and tells him that she has seen her parents die in flames. She was betrothed to a man whom she didn't love before her village was destroyed. Now, she has no future except to sell herself at Dreamland ("This Money's Yours"). Chris asks her to live with him, and they express their love for each other ("Sun and Moon"). As they part ways, she says that she will bring friends to bless their room with paper unicorns and perfume in keeping with her traditions ("Unicorn").

Chris calls John at the Embassy where they both work to tell him that he needs time to spend with Kim. John says that Saigon is falling apart and urges him to come to the Embassy right away, or he could get left behind ("Telephone Sequence"). Chris then goes to the Engineer and bargains with him for another night with Kim. The Engineer insists that he will only trade Kim for a visa from the American Embassy, but Chris refuses and will only pay him money ("The Deal"). Gigi and the other bar girls are helping Kim move in with Chris. They sing a song that is traditionally sung at weddings and all toast to the couple, calling Kim the new Miss Saigon ("The Wedding"). In the midst of their celebration, the door flies open, and Thuy, Kim's fiancé, appears. He has come to claim Kim and save her from the shame of being a bar girl. When he sees Chris, he becomes outraged. Kim tells him that her parents' promises died with them, and she will not abide by their arranged marriage. He leaves ("Thuy's Intervention"). Chris reveals to Kim that he has decided to bring her with him to America. They promise each other that everything will be different now that they will be together in America ("Last Night of the World").

Three years pass. The Viet Cong have taken over Saigon. The Engineer is brought in by two soldiers. We learn that he was taken prisoner by the Viet Cong and has been forced to work in the rice fields. Although his captors attempted to brainwash him, they have been unsuccessful. He is led before Thuy, who is now a Commissar. Thuy demands the Engineer's assistance in finding Kim and gives him 48 hours to accomplish this deed ("The Morning of the Dragon"). Kim is living in a small room, which she shares with a group of other Vietnamese. She remembers her moments with Chris and fiercely believes that he will come back to her. Meanwhile, in America, Ellen, who is now married to Chris, sits beside her sleeping husband on their bed, watching her husband have a nightmare and cry out names that she doesn't know. She knows that he has secrets and a dark past, but she vows to remain his wife and help him through his troubles. A world away, Kim — alone in a room full of strangers — makes the same vow ("I Still Believe").

The Engineer appears with Thuy. Thuy wants to forget Kim's transgression and marry her, as their parents decreed. She says that she is still bound to Chris. Thuy calls her a fool and summons his men into the room, where they threaten Kim and the Engineer. Thuy again demands that Kim agree to his wishes. The Engineer is sent out of the room, and Kim reveals her secret to Thuy: her two year old son, Tam ("Coo-Coo Princess"). Thuy says that she can't keep the child, since he intends to marry her. He calls the child his enemy and draws out his knife to kill the little boy. Kim pulls out a gun and threatens to shoot him. He will not relent, so she kills him ("Thuy's Death").

Kim is horrified but decides that she and Tam must find a way to reach Chris in America. The Engineer is making his way through the city. He finds his way to the remains of Dreamland and opens a trap door. There, he finds a box of counterfeit watches that he had hidden. Planning to sell them in Bangkok and then travel to the United States, he is about to leave when Kim appears ("If You Want to Die in Bed"). She begs for his help, and he realizes that the baby is their passport to America. ("Kim & Engineer"). He leaves to buy their passage on a boat to Bangkok. Kim consoles Tam and promises him that she will risk anything for him. The Engineer, Kim and Tam join a group of Vietnamese refugees ("Finale Act I").

Act Two

John now works on behalf of Bui-Doi children, the children of American and Vietnamese, who were conceived during the war. He is speaking about the plight of these children to a group of men ("Bui-Doi"). The images in the film of the small, forgotten victims reach out to haunt the veterans of the war, including Chris, who has been summoned to the conference by John. Chris learns that Kim has escaped to Bangkok and that he is the father of her two-year-old son. Chris is distraught; believing that he would never see Kim again, he has married Ellen. John suggests that Chris tell Ellen the truth, then they can go to Bangkok together to face the situation ("Post Bui-Doi").

In Bangkok, the Engineer has landed a job as the doorman and barker at a sleazy nightclub. John arrives, and the Engineer leads him to Kim. John tries to tell her the truth about Chris, but she insists on showing off her son ("Bangkok"). John is torn between telling her the truth and allowing Chris to tell Kim about his marriage. He tells her that Chris is in Bangkok and that he will come to see her ("Please"). When John leaves, the Engineer tells Kim not to wait for Chris to come to her, but to go to his hotel at once. She prays to her parents for their blessing, and the Engineer leaves to find out where Chris is staying ("Chris Is Here"). As she waits for the Engineer, Kim falls asleep. Thuy's ghost appears to haunt her. He asks her where Chris was on the night that Saigon fell ("Kim's Nightmare – Part 1") and we travel back to the past that she remembers: after securing a visa so that she could return to the United States with him, Chris left her in their room with a gun and went to work at the embassy with a promise that they would have plenty of warning for escape; when he reaches the embassy, however, he is told to evacuate immediately and forbidden to return for Kim ("Kim's Nightmare – Part 2"). The embassy is a wild scene, with mobs of Vietnamese pounding at the gates, begging to be evacuated. Kim comes to the gate just as the order is issued that no more Vietnamese can enter the grounds. Although Chris and Kim struggle to reach each other, their efforts are in vain. He is forced to board the last helicopter to leave Saigon ("Kim's Nightmare – Part 3").

Kim wakes up from her nightmare ("Sun & Moon – Reprise"). The Engineer brings the address of the hotel at which Chris is staying, and Kim runs through the city to find him. At the same time, John is bringing Chris through the streets to find her. At the hotel, Ellen answers the door and, for a moment, both women are confused. However, Ellen soon realizes who Kim is and reveals her marriage to Chris. As the truth sinks in, Kim insists that Ellen and Chris must take Tam back to America with them. Ellen refuses, saying that Tam belongs with Kim, but Kim is desperate for her son to have a better life in America. Kim leaves, insisting that Chris must come to see her ("Kim & Ellen"). Ellen is very upset at having met Kim and feels that part of Chris will always love her ("Now That I've Seen Her").

Chris and John return, and Ellen confronts Chris with her doubts about his love. He then explains that his relationship with Kim happened when he was a deeply confused man; only with Ellen did his life begin again. They reaffirm their love for each other. John, however, reminds them that they must resolve Tam's future; Chris suggests that Kim and Tam remain in Bangkok with his financial support because Ellen could not accept the idea of having Kim in the United States, but John knows that Kim will not accept the idea of having Tam stay in Bangkok. He urges them to reconsider ("Chris & Ellen").

Outside, Kim is promising Tam that he will have a new life in America. She knows that Chris will come for his son. She goes back to the club and lies to the Engineer, saying that Chris is coming for them that night. She says that the Engineer must pack his things and prepare for the journey to America ("Paper Dragons"). The Engineer rejoices at finally being able to go to America and having his dreams come true ("The American Dream"). Kim dresses Tam in his best clothes. She tells him that his father is coming to take him home. She kisses Tam and hears Chris and the Engineer approaching. She gives Tam a toy and sends him out to join the Engineer. She takes Chris' gun out of her bedside table and, as Tam goes to the others, she turns the gun on herself and shoots. Chris bursts in just as Kim is dying. He holds her in his arms as the tragedy unfolds and the curtain falls ("Finale Act 2").