New York City’s Times Square is a busy scene where three gamblers—Benny Southstreet, Nicely-Nicely Johnson, and Rusty Charlie—sing about their horseracing bets. Sergeant Sarah Brown and the band from Save-a-Soul Mission enter playing a hymn. Sarah delivers a street sermon and invites all sinners to visit the mission and repent before it is too late.
Nathan Detroit, another gambler, is having difficulty finding a location for his notorious floating craps game, which police Lieutenant Brannigan is always on the lookout for. Nathan mentions that he has found a place that might work, but he needs $1,000 to secure it. But Nathan is so broke he doesn’t even have money to buy an engagement anniversary present for Miss Adelaide, his fiancée of fourteen years who doesn’t approve of his gambling activities.
Word has it that high roller Sky Masterson is in town. Nathan knows Sky will bet on almost anything, so he comes up with a way to trick Sky out of the $1,000 for the game. Sky enters and, suspecting Nathan is up to something, refuses the bet. Instead he tells Nathan that Miss Adelaide is the one with the upper hand and has trapped him into marrying her. When Nathan asks why he is traveling on to Havana alone, Sky says he could get any woman he wanted to go with him. Nathan bets him $1,000 that he can pick a woman that Sky can’t convince to go. Just then he points to Sarah Brown as the Mission Band comes by. Sky takes him up on the bet and Nathan works to secure the location for the craps game.
After a night of preaching on the street, Sarah goes back to Save-a-Soul Mission when Sky enters and eagerly presents himself as a sinner. He impresses her with his knowledge of the Bible (from years of living in hotels where Gideon Bibles were handy). He notes the absence of sinners in the mission and offers her his marker, an IOU promising twelve sinners for the mission, if she agrees to have dinner with him at his favorite restaurant—in Havana. Insulted, she throws his marker in the trash and asks him to leave. He accuses her of hating men, which she denies and they sing about how they’ll know when the right person comes along. Caught up in the moment, they kiss, and then, appalled, Sarah slaps Sky.
After her performance at the Hot Box nightclub, Miss Adelaide tells Nathan that they can finally get married because she is getting a raise. Nathan comes up with more reasons not to get married. When one of Adelaide’s chorus girlfriends complains that her date cancelled because of the craps game, Nathan rushes off, and Adelaide starts one of her chronic sneezing attacks that she blames on being engaged for fourteen years.
At the mission, General Cartwright announces to Sarah that they will be closing the mission due to not attracting enough sinners. Just then Sky retrieves his marker from the trash and gives it back to Sarah who in turn guarantees the general that she will have twelve sinners the following evening.
Sarah and Sky fly to Havana for dinner. When she orders a milkshake, Sky translates it to the waiter as a “dulce de leche,” an alcoholic drink. Sarah loves the flavor, has a few too many, and gets herself into a barroom brawl. Before leaving Havana, Sky and Sarah express their newfound feelings for each other.
When they return home, they discover the gamblers have been holding their craps game in the mission since Nathan could not get the $1,000 from Sky. Sarah is furious and is convinced that their trip to Havana was simply part of the scheme for the craps game. Adelaide, too, is upset that Nathan is still running the game and breaks things off with him. Sky tells Sarah that he still intends to honor his IOU for sinners.
The rest of the craps game ends up in taking place in the sewer. Sky takes on Big Julie, a gangster-type who has taken over the game. Sky proposes a bet with one throw of the dice that he’ll either pay each gambler $1,000 or they all must accompany him to a prayer meeting that night.
Who will luck favor? And what are Sarah and Adelaide going to do about these gamblers, their feelings for them, and their futures together? Somehow, this fun musical provides the perfect venue for these guys and dolls to figure it all out.