Act I
A pantomime of never-ceasing activities depicts the hustle and bustle of New York City ("Runyonland"). Three small-time gamblers, Nicely-Nicely Johnson, Benny Southstreet, and Rusty Charlie, argue over which horse will win a big race ("Fugue for Tinhorns"). The band members of the Save-a-Soul Mission, led by the pious and beautiful Sergeant Sarah Brown, call for sinners to "Follow the Fold" and repent. Nicely and Benny's employer, Nathan Detroit, runs an illegal floating crap game. Due to local policeman Lt. Brannigan's strong-armed presence, he has found only one likely spot to hold the game: the "Biltmore garage". Its owner, Joey Biltmore, requires a $1,000 security deposit, and Nathan is broke ("The Oldest Established"). Nathan hopes to win a $1,000 bet against Sky Masterson, a gambler willing to bet on virtually anything. Nathan proposes a bet he believes he cannot lose: Sky must take a woman of Nathan's choice to dinner in Havana, Cuba. Sky agrees, and Nathan chooses Sarah Brown.
At the mission, Sky attempts to make a deal with Sarah; offering her "one dozen genuine sinners" in exchange for the date in Havana. Sarah refuses, and they argue over whom they will fall in love with ("I'll Know"). Sky kisses Sarah, and she slaps him. Nathan goes to watch his fiancée of 14 years, Adelaide, perform her nightclub act (“A Bushel and a Peck”). After her show, she asks him to marry her once again, telling him that she has been sending her mother letters for twelve years claiming that they have been married with five children. She finds out that Nathan is still running the crap game. After kicking him out, she reads a medical book telling her that her long-running cold may be due to Nathan's refusal to marry her ("Adelaide's Lament").
The next day, Nicely and Benny watch as Sky pursues Sarah, and Nathan tries to win back Adelaide's favor. They declare that guys will do anything for the dolls they love ("Guys and Dolls"). General Cartwright, the leader of Save-a-Soul, visits the mission and explains that she will be forced to close the branch unless they succeed in bringing some sinners to the upcoming revival meeting. Sarah, desperate to save the mission, promises the General "one dozen genuine sinners", implicitly accepting Sky's deal. Brannigan discovers a group of gamblers waiting for Nathan's crap game, and to convince him of their innocence, they tell Brannigan their gathering is Nathan's "surprise bachelor party". This satisfies Brannigan, and Nathan resigns himself to eloping with Adelaide. Adelaide goes home to pack, promising to meet him after her show the next afternoon. The Save-A-Soul Mission band passes by, and Nathan sees that Sarah is not in it; he realizes that he lost the bet and faints.
In a Havana nightclub, Sky buys a drink for himself and a "Cuban milkshake" for Sarah. She doesn't realize that the drink contains Bacardi rum, and she gets drunk and kisses Sky ("If I Were a Bell"). Sky realizes that he genuinely cares for Sarah, and he takes her back to New York. They return at around 4:00 a.m., and Sky tells Sarah how much he loves the early morning ("My Time of Day"). They both spontaneously admit that they're in love ("I've Never Been in Love Before"). A siren sounds and gamblers run out of the mission, where Nathan has been holding the crap game. Sarah assumes that Sky took her to Havana so Nathan could run the game in the mission, and she walks out on him.
Act II
The next evening, Adelaide performs her act ("Take Back Your Mink"). Nathan doesn't show up for the elopement because he's still running the crap game. She soon realizes that Nathan has stood her up again ("Adelaide's Second Lament").
Sarah admits to Arvide, her uncle and fellow mission worker, that she does love Sky, but she will not see him again. Arvide expresses his faith in Sky's inherent goodness and urges Sarah to follow her heart ("More I Cannot Wish You"). Sky tells Sarah he intends to deliver the dozen genuine sinners for the revival. She doesn't believe him and walks off, but Arvide subtly encourages him.
Nicely shows Sky to the crap game; now in the sewers ("Crapshooters Dance"). Big Jule, a gambler, has lost a large sum of money and refuses to end the game until he earns it back. Sky arrives and fails to convince the crapshooters to come to the mission. He gives Nathan $1,000 and claims that he lost the bet to protect Sarah. Sky makes a last-minute bet to get the sinners; if he loses, everyone gets $1,000, but if he wins, they go to the mission ("Luck Be a Lady"). He wins the bet. Nathan runs into Adelaide on his way there. She tries to get him to elope, but when he can't, she walks out on him. Nathan professes his love for her ("Sue Me"), then leaves.
Sarah is shocked to see that Sky carried through on his promise. The General asks the gamblers to confess their sins, and while some do, one of them admits the real reason they are even there. The General is thrilled that good can come from evil. Attempting to appear contrite, Nicely invents a dream that encouraged him to repent, and the gamblers join in with revivalist fervor ("Sit Down, You're Rockin' the Boat"). Brannigan arrives and threatens to arrest everyone for the crap game in the Mission, but Sarah clears them, saying that none of the gamblers were at the mission the previous night. After Brannigan leaves, Nathan confesses that they held the crap game in the mission. He also confesses to the bet he made with Sky about taking Sarah to Havana. He adds that he won the bet, to Sarah's shock, and she realizes that Sky wanted to protect her reputation and must genuinely care about her.
Sarah and Adelaide run into each other, and they commiserate and then resolve to marry their men anyway and reform them later ("Marry the Man Today"). A few weeks later, Nathan owns a newsstand and has officially closed the crap game. Sky, who is now married to Sarah, works at the mission band and has also stopped gambling. The characters celebrate as Nathan and Adelaide are married ("Guys and Dolls (Finale/Reprise)").
