The central character, MacHeath? (Mack the Knife), a highwayman of some renown, marries Polly Peachum. This displeases her father, Jonathan Peachum, who controls the beggars of London, and he endeavours to have MacHeath? hung. This is somewhat complicated by the fact that the chief of police, Tiger Brown, is an old friend of MacHeath?'s. Peachum exerts considerable political influence and eventually MacHeath? is arrested and imprisoned, escapes, then imprisoned once more. At the point of execution, he is pardoned and given a baronetcy.
The play challenges conventional notions of property, and, to paraphrase from the play, asks the central rhetorical question: "Who is the bigger criminal? He who robs a bank or he who founds one?"
Interestingly, when this play was translated into French, it was retitled "The Fourpenny Opera".