Peachum, a fence and thief-catcher, justifies his actions. Mrs. Peachum, overhearing her husband's blacklisting of unproductive thieves, protests regarding one of them, Bob Booty (the nickname of Robert Walpole). The Peachums discover that Polly, their daughter, has secretly married Macheath, the famous highwayman, who is Peachum's principal client. Upset to find out that he will no longer be able to use Polly in his business, Peachum and his wife ask how Polly will support such a husband "in Gaming, Drinking and Whoring." Nevertheless, they conclude that the match may make sense if the husband can be killed for his money. They leave to carry out this errand. However, Polly has hidden Macheath.
Macheath goes to a tavern where he is surrounded by women of dubious virtue who, despite their class, compete in displaying perfect drawing-room manners, although the subject of their conversation is their success in picking pockets and shoplifting. Macheath discovers, too late, that two of them (Jenny Diver, Suky Tawdry) have contracted with Peachum to capture him, and he becomes a prisoner in Newgate prison. The prison is run by Peachum's associate, the corrupt jailer Lockit. His daughter, Lucy Lockit, has the opportunity to scold Macheath for having agreed to marry her and then broken this promise. She tells him that to see him tortured would give her pleasure. Macheath pacifies her, but Polly arrives and claims him as her husband. Macheath tells Lucy that Polly is crazy. Lucy helps Macheath to escape by stealing her father's keys. Her father learns of Macheath's promise to marry her and worries that if Macheath is recaptured and hanged, his fortune might be subject to Peachum's claims. Lockit and Peachum discover Macheath's hiding place. They decide to split his fortune.
Meanwhile, Polly visits Lucy to try to reach an agreement, but Lucy tries to poison her. Polly narrowly avoids the poisoned drink, and the two girls find out that Macheath has been recaptured owing to the inebriated Mrs Diana Trapes. They plead with their fathers for Macheath's life. However, Macheath now finds that four more pregnant women each claim him as their husband. He declares that he is ready to be hanged. The narrator (the Beggar), notes that although in a properly moral ending Macheath and the other villains would be hanged, the audience demands a happy ending, and so Macheath is reprieved, and all are invited to a dance of celebration, to celebrate his wedding to Polly.