Cymbeline, which takes places in ancient Britain, is filled with hidden identities, extraordinary schemes, and violent acts. Long ago, the two sons of King Cymbeline were abducted, leaving Cymbeline with a daughter, Imogen. Cymbeline's stepson, Cloten, is now his heir, and Cymbeline expects Imogen to marry him. She secretly marries Posthumus Leonatus instead.

Banished from court, Posthumus makes a foolish bet on Imogen's chastity, which leads to false evidence that she has betrayed him. He plots to have her killed, and starts by sending her on a journey. Meanwhile, still angry about Imogen's marriage, Cloten plans to find and rape her.

Imogen—now disguised as a boy, "Fidele"—unwittingly encounters her brothers, who have grown up in a mountain cave unaware of their princely origins. The brothers kill Cloten, but Imogen, horrified, believes they have slain Posthumus.

Cymbeline, meanwhile, refuses to pay a tribute to the Romans, who invade Britain. After the Romans are repelled in battle, Cymbeline agrees to the tribute, his sons are restored, and Imogen and Posthumus are reconciled.