He succeeds in escaping from the plantations, and has become the leader of a band of pirates, under an assumed name, and disguised as a black man.

Jenny Driver is now his mistress (presumably he has forgotten her treachery in 'The Beggar's Opera').

Polly sails across the ocean to find him, but is entrapped by Mrs.Trapes, a procuress, who sells her to Ducat, a rich merchant.

Mrs.Ducat, who is jealous, helps Polly to escape; she assumes a boy's dress and continues her search for Macheath.

She is captured by the pirates, and she and Macheath meet, neither recognising the other.
The pirates are attacking the English settlement; the Indians are helping the settlers.