A notorious thief fights for the right to marry the beggar king's daughter.

As he is leaving Jenny at the doors of a brothel, Mackie Messer, a pimp and gangster, sees Polly Peachum, the daughter of the king of beggars, on the street with her mother and immediately invites them into a local pub for a drink. He has already decided that he will marry Polly and instructs his men to steal a wedding dress and a complete set of home furnishings, including a grandfather clock. He orders them to invite Tiger Brown, the chief of police to the ceremony. While one of Mackie's men dances with Mrs. Peachum, Mackie and Polly come to an understanding. That evening Polly and Mackie are married, and Brown is one of the guests. Every beggar in London owes allegiance to Peachum; no one can beg without a license from the king of beggars. Peachum is furious when he learns of Polly's marriage, and out of revenge, he demands that Brown arrest Mackie. When Brown refuses, Peachum threatens to disrupt the approaching coronation of the English queen, which will cost Brown his job. When Polly learns of her father's actions, she warns Mackie to go into hiding, asking him to stay away from other women, particularly those in the brothel. Mackie turns over his business to Polly, but he has no intention of passing up his regular visit to Jenny. Knowing his habits, Mrs. Peachum brings the police to the brothel to wait for Mackie. She tells Jenny of Mackie's marriage and asks her to betray him. Angered by the news, Jenny signals to the police when Mackie arrives, but has a change of heart and helps him escape over the roofs. He hides with another prostitute, but the police capture him when he leaves her room. Meanwhile, under Polly's leadership, Mackie's gang has taken over a bank; from now on they will rob people legally. Peachum, believing that Brown was responsible for Mackie's escape, organizes the beggars. When Mrs. Peachum tells him that Polly is now married to a bank president, he tries to stop the demonstration, but the poor people have organized and no one can stop them. The demonstration stops the coronation. Feeling remorse for her part in Mackie's imprisonment, Jenny helps him escape. Mackie and Brown take refuge in the bank and reminisce about their service as soldiers in the Indian army. Having lost power over his beggars, Peachum comes to Mackie and asks to to join in his future exploits.