Lorenzo and Jessica lounge in moonlit Belmont. Trying to outdo each other, they flirt, comparing themselves to famous lovers of classical legend: Troilus and Cressida, Pyramus and Thisbe, Dido and Aeneas, and Medea and Jason.
While the setting seems idyllic and full of love, if you read between the lines the references actually suggest the perils of love: things end badly for each of the couples named.
A messenger enters with news that Portia will be back before daybreak from the monastery. He asks to know whether Bassanio has returned yet. Lorenzo says that they have received no word for him. Launcelot enters, with news that Bassanio will be back before morning. Lorenzo tells the servants to prepare for Portia's arrival, and to bring out music for Jessica and him to enjoy in the meantime. While they listen, and Lorenzo rhapsodizes about the beauty of the night and the music of the spheres (music generated by the movement of the stars), which, he says, can tame even wild beasts.
The rush of messengers begins the reconciliation and conclusion scene that will end with the marriages of the major characters. Lorenzo's commentary on the stars and the music of the spheres indicates that be believes that the universe is beautiful and ordered by a divine law, and suggests that the dark forces of anger and brutality, which Shylock represents, have been tamed.
Portia and Nerissa approach Belmont, and Portia admires the candlelit beauty of the estate, saying: "How far that little candle throws his beams! / So shines a good deed in a naughty world" (5.1.89–90) As the music dies down, Lorenzo recognizes Portia's voice and welcomes her home. She asks whether Bassanio and Gratiano have yet returned. Lorenzo replies that they have not, but that a messenger has come to announce that they are coming soon. Portia sends Nerissa into the house to instruct the servants not to give any sign of their having been absent. She tells Lorenzo and Jessica that they, too, must keep this secret to themselves for the time being.
Portia's comment about the beauty of her estate in the moonlight seems to be the exact opposite of Lorenzo's. While Lorenzo sees the world as naturally good, Portia sees it as naturally "naughty." Once she reaches the castle, Portia begins to coordinate the last stages of her dramatic trick involving the rings, reminiscent of how she coordinated the casket-picking scene and the scene in the courtroom.
At that moment, Bassanio, Antonio, and Gratiano enter. Portia welcomes Bassanio home; Bassanio introduces Antonio and asks her to "give welcome" to the friend to whom he is "so infinitely bound" (5.1.133–5). Welcoming Antonio, Portia jokes that she hopes Bassanio is only metaphorically bound to him because, last she has heard, Antonio was bound to his friend by a very dangerous contract indeed.
Now that Antonio's trial is over, Portia's hospitality renews the bonds of friendship between the Christian Venetians. Portia word play regarding the word "bound" references the theme of reading and interpretation that dominated the casket and courtroom scenes.
Nearby, Nerissa and Gratiano begin to argue over Gratiano's missing ring. Gratiano swears to Nerissa that he gave the ring to a judge's clerk. Portia asks what's wrong. Gratiano replies that his wife is overreacting. Nerissa insists that it is not the value of the ring but the fact that he broke his oath to keep it that upsets her. Portia joins in reprimanding Gratiano; she says, she gave her love such a ring as well, and made him swear never to part with it, and she is sure he never would. Gratiano blurts out in protest that Bassanio did give his ring away, to a judge who had earned it, and asked for it.
This final trick draws attention to the dimension of exchanging gifts, a kind of economy that lies beneath supposedly spontaneous love (of the kind that Jessica and Lorenzo were talking about at the beginning of this scene). As in other scenes of interpretation, Shakespeare draws the process of discovery out for dramatic effect.
Bassanio admits it is true. Portia pretends to be furious. She swears that she will never go to bed with Bassanio until she sees the ring. Despairing, Bassanio tries to defend himself and beg Portia's forgiveness, but Portia stays firm. She insists that she will give everything she has, including her body, to the man who has the ring. Nerissa vows to Gratiano that she will do the same. Bassanio continues to plead for forgiveness. He says, if Portia will only forgive him this once, he will never again break an oath with her. Antonio supports Bassanio, saying that he will be bound for his friend once more, and offer his soul as collateral because he is so certain that Bassanio will never again deliberately betray Portia.
The ring subplot really starts to take shape. The women's lie that they slept with the judge and law clerk to regain the rings makes the sexual connotations about rings (as symbols of female genitalia) more explicit. And once again, when Bassanio is in trouble, Antonio offers everything to help him. This time Antonio offers his soul in exchange for Bassanio's happiness, echoing his earlier deal with Shylock in which he offered his body in exchange for Bassanio's happiness.
Portia accepts the deal. She hands Antonio the ring, which she pretends is a different ring, and tells him to give it to Bassanio and to tell Bassanio not to lose it. When he sees the ring, Bassanio is stunned to see that it's the same one he gave to the lawyer! Portia explains that she got it from that very lawyer by sleeping with him, and asks for her husband's pardon. Nerissa does the same, explaining to Gratiano that she got her ring back by sleeping with the clerk the previous night. But before the shocked husbands can get too angry, Portia interrupts. She hands over a letter from Bellario in Padua, explaining that Portia was the lawyer who appeared in the Venice courtroom, and Nerissa the clerk. She calls upon Lorenzo to testify to the fact that she has only just returned. He does.
As in the casket scene, and the court scene, Portia once again coordinates and manages the other characters so that they end up interpreting things the way she wants them to. This time, she gets Bassanio and Gratiano to believe that their failure to keep their oaths resulted in their wives' infidelity. However, after having her fun, Portia starts to wrap things up, neatly reinstating the customary boundaries of legal marriage—faithfulness, fidelity, and so on.
Portia also has a letter for Antonio with even better news: three of his ships have suddenly come to harbor, full of riches. Then, Portia tells Lorenzo that her clerk—Nerissa—has good news for him as well. Nerissa reports: she has a deed from Shylock, leaving all of his property to Lorenzo and Jessica when he dies.
To modern audiences, the Christian characters' delight at just how fully they have plundered the ruined Shylock may seem a bit distasteful in this otherwise happy scene. It reflects how strongly their prejudices persist.
Finally Portia encourages everyone to go into the house to hear the full explanation of all these events. Gratiano jokes that he is not sure whether Nerissa wants to go to bed for two hours, or stay up and wait for the next night: he himself cannot wait to sleep with the doctor's clerk. For "while I live," he finishes, "I'll fear no other thing / So sore, as keeping safe Nerissa's ring" (5.1.306–7).
By ending on Gratiano's crude sexual joke (the ring as a symbol for the vagina), the play hits a comic final note but also calls into question how admirable the "good" characters in this play really are. How are their glee at destroying Shylock and their crude sexual jokes any better than Shylock's love of money and thirst for revenge?