It is a moonlight night at Belmont, and Lorenzo and Jessica are on the avenue leading to Portia's house. In the still evening air, the newlyweds are jokingly comparing this night to nights when other lovers — Troilus, Thisbe, Dido, and Medea — all committed romantic acts of love and daring. Lorenzo reminds Jessica that this night is very much like the night when he "stole" Jessica away, and she reminds him that on just such a night as this, Lorenzo swore his vows of love to her. She boasts that she could surpass him in producing other examples of other lovers, but she hears someone approaching. It is Stephano, who brings them news that Portia, accompanied by Nerissa, will arrive "before break of day." Launcelot then comes in, dancing and "hooloaing" and "sollaing" that his master Bassanio will arrive before morning, and he exits.
Lorenzo asks Stephano to have the musicians come outdoors and play. Silently, Portia and Nerissa enter and pause to listen. Portia remarks that music heard at night "sounds much sweeter than by day." Lorenzo hears Portia's voice and recognizes it immediately. He welcomes her home, and Portia gives orders that no one is to mention her absence. Then, as dawn is about to break, a trumpet announces the arrival of Bassanio, Antonio, Gratiano, and their followers.
Portia and Bassanio immediately exchange loving greetings, and Bassanio introduces his friend Antonio, who is graciously welcomed. Their conversation, however, is interrupted by a quarrel between Nerissa and Gratiano over the wedding ring which she gave him, and which he now confesses to have given to a "judge's clerk," a half-grown youth no taller than Nerissa. Portia tells Gratiano that he was at fault to give away his "wife's first gift." She is confident that Bassanio would never, for any reason, part with the ring which she gave him. Angrily, Gratiano tells her that Bassanio did indeed give away his wedding ring; in fact, he gave it to the "judge that begg'd it," just as he, Bassanio, gave his ring to the judge's clerk. Both wives pretend shock and anger, and they vow never to sleep with their husbands until they see their wedding rings again. Bassanio pleads in vain that he gave his ring for good reason to the lawyer who saved Antonio's life. Well, says Portia, since you have been so generous to him, if that lawyer comes here, "I'll have [him] for my bedfellow." "And," adds Nerissa,"I his clerk."
Antonio is terribly disturbed as he witnesses Portia's fury; he feels that he is "the unhappy subject of these quarrels." Bassanio then swears that if Portia will forgive him this time, he will never break a promise to her again. Antonio speaks up and offers his soul as forfeit, as before he offered his body, in support of Bassanio. Portia accepts Antonio's soul as security for Bassanio's word. "Give him this [ring]," she tells Antonio, "and bid him keep it better than the other." In amazement, Bassanio recognizes it as the same ring which he gave the lawyer. Nerissa then returns Gratiano's ring to her husband, who receives it in similar amazement.
Portia then explains that it was she who was the lawyer Balthasar at the trial of Antonio, and Nerissa was her clerk; they have just returned from Venice. For Antonio, she has a letter containing good news — three of Antonio's ships have safely come into port. Antonio reads the letter himself and is ecstatic: "Sweet lady, you have given me life and living," he says. Nerissa then presents Shylock's deed to Lorenzo and Jessica, bequeathing them all of his possessions.
"It is almost morning," Portia observes, and it will take time to explain how all these things happened. "Let us go in," she says, and she and Nerissa will answer all questions.
Act IV was given over almost entirely to the threat posed to the romantic love theme and was dominated by the figure of Shylock. In the play's last act, consisting of only this scene, we return to Belmont — the world of comedy and romance. The opening dialogue between Lorenzo and Jessica reestablishes the atmosphere of harmony.
Lorenzo's opening words call upon us to imagine that the lovers are surrounded by night and moonlight, "when the sweet wind did gently kiss the trees." Their dialogue is used to create the general atmosphere of love and night and moonlight, thus establishing the tone of the scene. Lorenzo introduces the theme of love and moonlight with two speeches of great beauty. In the early lines of the act (55-65), he introduces the idea that music is the "music of the spheres." This was a popular Elizabethan notion, according to which the revolution of each planet around the earth produced a sound, and the combination of all the individual sounds of the planets made a "divine harmony."
Lorenzo's next speech also concerns music. Having summoned Portia's own personal musicians, he signals them to play, and he elaborates on the nature of music to Jessica. Significantly, music is very often an important element in Shakespeare's plays, both as a theatrical device and also as a general criterion of character. Those characters who dislike music are invariably incomplete or distorted human beings. Here, Lorenzo underlines the idea that "the man that hath no music in himself . . . Let no such man be trusted."
The arrival of Portia and Nerissa, and then of Bassanio, Gratiano, and Antonio, sets in motion the final movement of the play: the denouement of the "ring story." Shakespeare has been quietly preparing us for this story as far back as Act III, Scene 2, when Portia presented her ring to Bassanio, "Which when you part from, lose, or give away, / Let be my vantage to exclaim upon you." The audience, of course, has been anticipating this development since the first scene of Act IV, when Antonio prevailed upon Bassanio to give the ring to "the young doctor of Rome."
After Bassanio, Antonio, and Portia converse sweetly together, Nerissa begins to take Gratiano to task, and their words suggest the beginning of a fairly violent disagreement. When Gratiano says, "By yonder moon, I swear you do me wrong," he invokes an air of injured innocence. One of the comic elements in what follows lies in the righteous confusion into which Bassanio and Gratiano are thrown. While they admit to having, for what seemed — at that particular time — to be the best of reasons, they did indeed part with their wedding rings. But they cannot understand their wives' furious accusations that they gave them to other women. Of course, in the comedies of ancient Greece and even in today's comedies, the sight of a man wrongly accused by his wife, yet totally unable to defend himself, is sure-fire comedy, and it is given a thorough workout here. As Nerissa berates Gratiano, Portia delivers her speech, with pious confidence, to the effect that her husband would never, on any account, part with the wedding ring which she gave him. Almost unconsciously, we wince in sympathy with Bassanio when he turns aside and says: "Why I were best to cut my left hand off / And swear I lost the ring defending it."
The element of the comedy here lies in the irony of many of the lines — that is, the knowledge which the two women have and the knowledge which the audience has and the knowledge which the two husbands do not have. This produces some lines which sound horrifyingly improper to the two husbands but are quite literally true. Portia says, for example, of the "doctor" to whom Bassanio gave the ring, that if he comes "near my house . . . I'll not deny him anything I have, / No, not my body nor my husband's bed. . . . I'll have that doctor for my bedfellow." To which Nerissa adds, sassily, "And I his clerk." And further, when they return the rings, Portia is able to affirm, "For by this ring the doctor lay with me," to which infidelity Nerissa is again able to add, the "doctor's clerk." By this time Bassanio and Gratiano have been teased enough, and the end of the scene is a succession of revelations: first, the true identity of the lawyer and his clerk, then of Antonio's good fortune, and finally, of Lorenzo and Jessica's inheritance.
Ending the comedy with the ring story serves two purposes. In the first place, Bassanio and Gratiano discover who Antonio's true saviors were. Second, and more important, there is always the threat of anticlimax at the end of a romantic comedy, when all the loose ends are tied up and the lovers are all reunited; suddenly, the "sweet talk" can become unbearably insipid. This is uniquely, usually, not the case with Shakespeare. He had a keen sense of the bawdy, and here he tempers his romantic scene with salty comedy in order to suggest that these lovers are very human lovers; their marriages will have their misunderstandings, but all this can be overcome with the aid of love and with another ingredient, a good sense of humor.