Here is a short plot summary of Cardenio*:
The Tyrant has usurped King Govianus and attempts to woo away The Lady, the sweetheart of Govianus. However, she vows loyalty to Govianus. Even under pressure from her father, Helvetius, to accept the Tyrant, she remains true to her lover. The Tyrant then imprisons her with Govianus and attempts to force her to love him. Refusing to give in she begs Govianus to kill her. He cannot because of his love for her. She then kills herself. The Tyrant, determined to have her, even if dead, removes her body from her tomb to reign as his queen.
Meantime, Anselmus, wishing to test his wife’s fidelity, asks his friend, Votarius, to attempt seduce her. But when he rendevous with The Wife, they fall in love. Worried that Anselmus will discover their affair, they form a plan. While Anselmus is within earshot, she will pretend to rebuff the advances of Votarius. To make it realistic she will wave a sword and perhaps even give Votarius a small wound. When the occasion arises she wields the sword to rebuff Votarius. A servant has poisoned the tip of the sword: she grazes Votarius skin, and he dies.
Govianus, in prison, has a vision of the ghost of The Lady. The ghost informs him of The Tyrant’s morbid preoccupation with her dead body. Govianus begins to plan his revenge. He is eventually released from prison and he puts his plan into action. He applies poison to the corpse’s lips then paints her face to make her appear to have come back to life. When The Tyrant sees her, he says, “O, she lives again!” He kisses her and he dies. The nobles proclaim Govianus the rightful king.
* Based on Lewis Theobald, 18th century playwright, who claimed that his play ‘Double Falsehood’ was based Shakespeare’s lost play ‘The History of of Cardenio’