Synopsis for Cymbeline

Cymbeline, king of Britain, has an evil second wife who wishes to see her own oafish son, Cloten, wedded to Cymbeline’s daughter, Imogen. But Imogen, against her father’s will, has married Posthumus Leonatus, who is banished; before parting he gives a bracelet to Imogen. Iachimo, in Rome, boasts to the angry Posthumus that Imogen is corruptible; later, in Britain, he arranges to be secreted in a trunk in her bed-chamber, and when she is asleep, he emerges and steals her bracelet. Posthumus, persuaded, vows to be revenged on Imogen. Writing to her to meet him at Milford Haven, he orders his servant, Pisanio, to kill her on the journey.
Rome demands from Britain tribute that the King refuses. Pisanio, faithful to the bewildered Imogen, tells her to disguise herself as a boy and seek the invading Roman general. Losing herself in Wales, she is sheltered under the name Fidele by a long-banished lord, Belarius, who calls himself Morgan, and two youths who are actually sons of the king (and Imogen’s brothers), stolen in infancy and brought up in a mountain cave. In sickness, Imogen/Fidele takes a sleeping drug that gives the appearance of death.
Cloten, in the clothes of Posthumus, has followed her with evil intent, but one of the youths meets and kills him. Returning, the brothers and Belarius find “Fidele” apparently dead; when she wakes, alone, she mistakes Cloten’s headless body for her husband’s. Profoundly grieved, she joins the Roman general, whose forces are ready to attack Cymbeline.
The courage of Belarius and the princes win the battle for Britain. All come at length before the king, and swiftly, one revelation growing from another, the plot is resolved. There is happiness for all except the dead Queen; Cymbeline magnanimously submits to Rome, and even Iachimo is pardoned, who has fought with the Romans. Imogen and Posthumus are reunited.

-The Pocket Companion to Shakespeare’s Plays by J C Trewin