Before the play begins...
Cymbeline, a king of ancient Britain, rules at the time of Augustus Caesar's great Roman Empire, a time in history associated with general peace and the birth of Jesus. Britain is part of the Roman Empire and living under Rome's protectorship. Cymbeline had two sons, stolen away at ages two and three, and a daughter, the Princess Imogen. Posthumus, a son of a valiant warrior but a commoner, is orphaned at birth. Raised by Cymbeline in the royal household, he and the Imogen fall in love. After his first wife's death, Cymbeline marries a wicked queen who has designs on the throne for her own son, Cloten. Imogen has rejected Cloten in favor of her Posthumus.
Cymbeline, enraged by his daughter's secret marriage to Posthumus, banishes him from Britain. In parting, the couple exchange symbols of their loyalty: Posthumus gives Imogen his bracelet, and she, in turn, gives him her diamond ring. Cymbeline and his Queen desire nothing more than the marriage of Imogen to the Queen's "clottish" son, Cloten, whom Imogen categorically rejects.
The banished Posthumus seeks refuge in Italy in the home of a family friend, Philario, where he meets Iachimo. Iachimo, a worldly Italian, scoffs at the young man's certainty of his wife's unwavering fidelity. Incensed, Posthumus rashly enters into a wager with Iachimo: Imogen's diamond ring will be Iachimo's if Posthumus's wife betrays him. Armed with a letter of introduction from Posthumus, Iachimo ventures to Britain, meets Imogen, and tries unsuccessfully to seduce her. Switching tactics, Iachimo begs Imogen's forgiveness and asks her to store overnight a treasure that he says belongs in part to her husband. Imogen agrees, and offers her bedchamber for the trunk's safekeeping.
Pisanio, the faithful servant to Posthumus and his bride, receives an herbal potion from the Queen as a gift that she hopes will murder either or both Pisanio and Imogen. But the good doctor Cornelius reveals to the audience that the potions he has entrusted to the Queen will impose no more than a death-like and temporary sleep.
At night, the trunk in Imogen's bedroom opens and reveals Iachimo. In lust he admires the sleeping princess, then steals Posthumus's bracelet from her wrist, and records minute details of the bedchamber and her body to serve as "proof" to Posthumus of his wife's infidelity. Iachimo returns to Italy and all too easily, convinces Posthumus that his wife has been unfaithful. Cloten continues his unwanted courtship of the Princess, who finally tells Cloten that her husband's poorest garments mean more to her than Cloten himself ever could. Cloten is enraged and plots revenge.
Lucius, the noble ambassador from Rome, comes to Cymbeline's court to demand the tribute that is due to Augustus Caesar. The defiant advice of his Queen and stepson lead Cymbeline to deny Rome its tribute and war between the two countries is declared. Writing to Pisanio, Posthumus orders his servant to murder the faithless Imogen. Pisanio is horrified by Posthumus's false claim, and instead the good servant devises a plan to re-unite the couple. He reveals her husband's letter to Imogen, and then arming her with a boy's disguise and the restorative" potions of the Queen, he sends her off to join the Roman army as a page to the noble Lucius. Pisanio believes that, once in Italy, Imogen can regain her estranged husband's trust. Imogen, dressed in boy's clothes, adopts the name "Fidele."
Lost in the Welsh hills, a frightened and hungry Imogen finds the shelter of an inhabited cave. The cave serves as the rustic home of Belarius, a nobleman banished unjustly from Cymbeline's court. As a fugitive, Belarius (alias Morgan) has lived in the hills for 20 years and raised as his own the King's lost sons, kidnapped in revenge as he fled the court. The boys, now named Guiderius and Arviragus, unaware of their true identities, have been raised as woodsmen and hunters. But they crave a wider world of adventure than the forest, despite their father's tales of corruption and villainy in the world of civilized society from which he has fled. Immediately upon meeting "Fidele," the boys feel an unaccountable affection for this boy who is, in fact, their sister.
Back at court, Cloten demands Posthumus' garments from Pisanio and, in his rival's disguise, sets out to Milford-Haven to seek his brutal revenge upon the couple.
In the woods, Cloten is greeted not by the fugitive couple as he intends, but by Belarius and his "sons," the princes of Britain. Insulted by Cloten, the fearless Guiderius beheads the arrogant stepson of the King. Meanwhile, Imogen, sick at heart, takes the potion that Pisanio has given her, and falls into a death-like sleep. Discovered by Guiderius and Arviragus, "Fidele" is presumed dead, and is placed beside the headless body of Cloten in a primitive burial.
Imogen awakes to find the headless body dressed as Posthumus beside her. At this moment of total despair, the Roman ambassador Lucius comes upon Fidele and welcomes the young "man" into his service. Against their father's wishes, Guiderius and Arviragus insist upon joining the war against Rome in their country's defense. Belarius decides to join them.
A remorseful Posthumus, believing his wife to be murdered by his own order, returns to Britain and, disguised as a British peasant, joins Belarius and the princes in the battle against Rome. A war completely lost is suddenly turned around and won by Britain due to the heroic feats of these four newcomers to the battle. Posthumus adopts another disguise and, as a defeated Roman, goes in search of a longed-for death at the hands of the victorious Britons. Imprisoned and awaiting death, he dreams of his dead parents, who plea to Jupiter on their son's behalf. Angered by the mortals' pleas, the god asserts that he is watching over the young man's destiny.
The Roman prisoners, including Lucius, Fidele, Iachimo and Posthumus in Roman dress, are brought before Cymbeline. Drawn by a mysterious affection he feels toward the young Roman page (who is, in fact, his daughter Imogen), the King grants him pardon and one wish. Fidele demands to know from Iachimo how the Italian came to possess the diamond ring he wore upon his hand (the same diamond that Imogen had given to her husband at their parting). Iachimo confesses his terrible guilt. Imogen reveals her identity, and the couple is reunited. The doctor announces the Queen's death and villainy. Belarius reveals his identity and the princes'—and the royal family is joyfully reunited. Cymbeline makes peace with Britain and pays Augustus Caesar due tribute.
– Contributed by the CST Education Department