Macheath lies in bed in the stable. Polly enters and tells him that her father has been to see Brown and that Macheath needs to leave immediately. Macheath is not scared and asks Polly to come join him in the bed. In an attempt to calm her, Macheath reminds her that he does not have a record at Scotland Yard. Polly protests that although he had no record the day before, after her father’s visit to Brown, he now has a long list of crimes, including murders, burglaries, robberies, arsons, and seducing two sisters under the age of consent. Macheath suavely says that the sisters told him they were twenty. Then he asks what Brown said, and Polly tells him that Brown said he could not help Macheath any longer.
Macheath realizes his situation is serious and that Polly will have to run the business in his absence. In a reversal of the first interaction in the scene, Polly now wants to take him to bed, but Macheath insists on talking business. He shows her all his ledgers and explains how to handle all his thieves. At first, Polly can barely think about such things and sobs throughout his instructions, but she eventually agrees to take responsibility. Macheath tells her to continue sending the profits to a banking house in Manchester and adds that he will soon be getting out of petty crime and into banking because it is safer and more profitable. His last instruction is that in two weeks Polly should put all the business’s money in the bank and turn in all of his thieves.
Just then, the thieves enter. Macheath explains that he has to leave. Matthew protests that it is a shame he has to leave when the coronation is coming. Macheath explains that Polly will be in charge while he is gone. Matthew continues to protest, and with Macheath’s prodding, Polly tears into him with a vengeance. There is a brief pause, and then all the men applaud her performance because they agree that she will make a fine crime boss. Before the criminals leave, Macheath reprimands Matthew for drinking too much. He says that last week Matthew took credit for setting the children’s hospital on fire. He asks all the men to tell him who set the hospital on fire. They all reply that Macheath did. The thieves exit.
Alone again, Macheath and Polly say their goodbyes. Polly worries that Macheath will be unfaithful while he is away. Macheath promises that he would never be unfaithful. Desperately in love, Polly asks him to stay. She is afraid that their love is coming to a close. She tells him about a dream she had the night before, in which she looked out the window and saw the moon that was the size of a faded penny. They kiss, and Macheath exits. Alone onstage, Polly says that he will never come back. She tells herself to tear her heart out and get over it. Then she questions why women should grieve when their mothers have already experienced grief. She asks the Virgin Mary to pity women. The bells marking the arrival of the queen begin to ring.
The scene emphasizes the characters’ trust for one another. Brown, who just a moment ago was swearing his friendship to Macheath, has now quickly folded under pressure from Peachum. Clearly he is not as loyal a friend as he had claimed, and Macheath hardly even expresses surprise. On the one hand, Macheath’s reaction to Brown’s betrayal is ironic because if the two were best friends, like Macheath says they are, he would feel the betrayal much deeper. On the other hand, this betrayal causes Macheath to trust his new wife. Based on what her parents told Polly before and from what she heard from the criminals, she knows to second-guess what Macheath tells her. However, she tries to believe him because she loves him. The list of Macheath’s previous wrongdoings sparks a conflict in Polly because she realizes Macheath is a criminal, but she will do anything to help him because of her feelings for him. Polly loves Macheath, but at the same time, she is unsure of whether she can trust him because Macheath did not reveal his past crimes to her. This trust Polly feels with Macheath demonstrates the conflict between self-interest and love.
This scene establishes Macheath as an ironic hero. As a literary technique, irony occurs when someone or something is the opposite from what was expected. In Macheath’s case, his charisma is undeniable: He dresses well, is sexually appealing, makes funny jokes, and has a good head for business. But at the same time, all of his actions are wrong by the moral standards of society. He kills, sleeps with underage girls, sells out his best friends to the law, and even actively takes credit for burning down a children’s hospital. Moreover, no effort is made to reconcile these aspects of Macheath, which makes his status as a hero ironic. Macheath never feels guilty for his crimes because to him, the crimes are simply business. The unreconciled incongruity between Macheath’s outward appearance and his behavior creates a strong sense of irony in The Threepenny Opera. He does the opposite of what a charming hero is expected to do. The irony generates the question of whether Macheath is a decent person forced to survive in a rotten world or if he is a rotten person who disguises his true being through charm. However, the play implies that perhaps there is no difference between those two perspectives. In a world in which even surviving requires trampling others, no one can be truly good at heart, and only the wealthy have the luxury of talking about morality.