In Britain, Cymbeline, the Queen, and Cloten meet with Caius Lucius, the Roman ambassador, who demands the continuation of a tribute that was begun in Julius Caesar's time. Britain pays this tribute in exchange for Rome's promise not to invade. Supported by his wife and stepson, Cymbeline refuses to pay it, declaring that Britain is an independent isle and will remain so--which leads Lucius to say, regretfully, that a state of war must exist between Rome and Britain.
Meanwhile, Pisanio has received a letter from Posthumus, accusing Imogen of infidelity and asking his servant to lead her away from London and murder her. Pisanio is horrified and cannot believe what he is being asked to do. Nevertheless, he begins to carry out his master's orders: He gives Imogen another letter, also from Posthumus, in which her husband asks her to meet him at Milford Haven, on the coast of Wales. Imogen is transported with joy at the thought of seeing him again, and she immediately makes preparations to slip away from her father's palace.
The scene now shifts to the wilderness of Wales, where an old shepherd named Belarius instructs his two sons, Guiderius and Arviragus, in the wonders of nature. The young men are restless because they have never been allowed to leave their wilderness home and see the wilder world; Belarius insists, however, that there is nothing in the city but treachery and wickedness, and he recounts how he was once a nobleman in Cymbeline's court but was banished for crimes he did not commit. When his sons exit the stage, he tells the audience that the boys are actually the sons of Cymbeline himself; Belarius kidnapped them when they were very young in order to avenge his unjust exile. They remain ignorant of their true identity, and they believe that Belarius's name is Morgan and that they themselves are named Polydore and Cadwal.
Imogen and Pisanio arrive in Milford Haven, and the Princess, seeing no sign of her husband, becomes perturbed. The unhappy servant then reveals the deception, and he shows her Posthumus's letter accusing her of infidelity. Imogen falls to weeping, cursing her husband's lack of trust in her, and she then begs Pisanio to follow his master's orders and kill her, since her life is no longer worth living. He refuses, however, and she asks why he bothered to bring her to Milford Haven if not to kill her. Pisanio replies that by maintaining the appearance of having followed through with the plan--by faking Imogen's death-- they may instill guilt in Posthumus and restore his love for her. Posthumus must have been deceived by some villain into thinking Imogen unfaithful; perhaps the villain, too, will become contrite upon hearing of Imogen's "death" and turn himself in. He, thus, suggests that she disguise herself as a boy, with clothes that he has brought for this purpose, and enter the service of Caius Lucius, who will soon be leaving England from the Milford Haven port. In this way, she can make her way to Italy, where Posthumus resides. She agrees to his plan, and she changes clothes--and as a parting gift, he presents her with the potion that the Queen gave to him, telling her what he believes to be true: It is a soothing cordial that will help her if she grows sick on the voyage.
The discussion between Cymbeline and Caius Lucius poses difficulties in interpretation: Shakespeare has his two villains, the Queen and Cloten, express what are typically considered noble sentiments. Both argue passionately for British independence from Rome, with a stirring patriotism that, in a different play, would make them sympathetic figures. One might argue that by allowing them these sentiments, Shakespeare is granting his villains a hint of three- dimensionality. On the other hand, later events in the play contradict this argument, when Cymbeline decides to resume paying tribute to Rome even after having defeated the Roman army--thus, proving that his ignoble behavior toward Rome had resulted solely from his wife's malignant influence over him. This current scene, then, may actually be intended to subvert the notions of British patriotism that dominate historical plays like Henry V, by placing them in the mouths of the wicked Queen and her idiot son. Yet again Cymbeline serves partially as a vehicle for Shakespeare to dabble in self-parody.
As the action shifts to the wilds around Milford Haven, Imogen begins to dominate the play, and after the embarrassment of Posthumus's ridiculous behavior, her sustained presence comes as a welcome relief. She is, as many critics have noted, the most attractive, appealing, and multifaceted character in the play--to such an extent, indeed, that she often seems out of place amid the lesser men and women around her. She is eloquent and passionate, yet (unlike Juliet, for example) she does not allow her passion obliterate her common sense. She is resourceful, too, as evidenced by her willingness to adopt Pisanio's rather risky plan and her ability to quickly grow accustomed to wearing boy's clothes. Indeed, a number of male critics have praised her as Shakespeare's perfect woman; it is difficult to find a flaw in her, and she is so well spoken that she never becomes boring. If there is a weakness in Imogen, it lies in the fact that she is almost too perfect; one might say that she more closely resembles a male fantasy than a convincing woman character.
Meanwhile, the subplot involving Cymbeline's missing sons, promised so early in the play, finally emerges in full with the appearance of Belarius and his adopted sons. They are introduced to us by Belarius' extended speech on the corruption of city life, which a number of critics have seen as an expression of the aging Shakespeare's own dissatisfaction with years spent wading in the politics of London's theatrical world. It should be noted, however, that as Guiderius points out, it is easy for the world-weary Belarius to talk about the wickedness of the world, but for his young and energetic sons, the wilderness life represents "a cell of ignorance (III.iii.33)." But whatever the playwright's own feelings, Guiderius and Arviragus ultimately win the debate and, over Belarius' cautious objections, escape from rural obscurity into the wider world--and the play rewards them for it: In doing so, they regain their birthright.