Deep in the heart of Soho the bandit Mac the Knife is celebrating his marriage to Polly Peachum, the beggar king's daughter.
Macheath, his bride Polly, and his friend Matthew enter an empty stable where they are to hold the wedding ceremony. Polly isn't impressed.
Suddenly Mac's friends show up with tons of furniture, dishes, and carpets, and set up the stable as though it were a luxurious room. They congratulate the bride and groom while they talk about all the people they hurt in order to get the stolen goods they're bringing in.
The vicar, Reverend Kimball, comes to marry the two, and they sing the song again. Polly, too, gets up and sings a song about being a pirate named Jenny who will murder everyone who ever looked down on her when her ship comes in.
Next the cops show up, but it's just the chief, Tiger Brown, coming to congratulate his old friend Mac on his wedding. They sing "The Cannon Song", about their old days as army buddies.
Jackie, which is Tiger's real name, tells Mac not to worry about anything, that there's nothing on record against him at Scotland Yard.
The men part a curtain and reveal a hidden bed, then leave the newlyweds to their honeymoon.