The Duke of Savoy was betrothed to Princess Leonora of Milan – but the current Milanese ruler has reneged on the commitment. The indignant Duke decides to court a local gentlewoman named Cleona instead. Foscari, Cleona's former betrothed, is believed dead; but he suddenly shows up in the Savoyard capital quite alive, and accompanied by a handsome young page called Dulcino, whom Foscari rescued from bandits. Foscari, unaware of the Duke's interest in Cleona, sends Dulcino to her to announce his arrival; the Duke meets Dulcino there, and is powerfully struck by the page's resemblance to Leonora. Cleona, for her part, is faithful to Foscari and pleased to learn he's alive and well.
Foscari, however, through an exaggerated sense of loyalty, resolves to resign his interest in Cleona to the Duke and decides to become a Benedictine monk. He informs the surprised Duke of his decision, and sends Dulcino to tell Cleona that the news that Foscari is alive is actually false. Foscari even convinces a hesitant Dulcino to join the Benedictine order along with him.[3] A monk named Valentio arrives to arrange their admission – but Valentio instantly greets Dulcino as "dear Leonora." Valentio reveals that Leonora had fled the Milanese court when her father died, for she feared being forced to marry her uncle. She disguised herself as a page and came to Savoy, with Valentio as her companion and chaperon, to see if the Duke would honor their previous commitment. Two weddings, of the Duke and Leonora and of Foscari and Cleona, determine the happy ending.
As usual in Shirley's drama, this main plot is supported by secondary material. The Duke has a libertine brother, Lodwick; at the start of the play his wife Astella has left him and is staying with Cleona. Lodwick commands his follower Piero to commit adultery with Astella, so that Lodwick can divorce her. Lodwick's old tutor, Lord Grimuldo, tries to persuade his former student to repent; failing this, Grimuldo pretends to have been testing Lodwick and to be, in reality, a fellow libertine. Grimuldo offers to introduce Lodwick to a superior mistress, and brings him to a lush garden filled with strange music, where they watch a masque of nymphs and satyrs. The woman Lodwick meets there is enticing but disturbing; she hints that she has unusual powers, and offers him unlimited dominion – and finally concedes that she is a devil, a succubus.
A deeply upset Lodwick flees homeward, only to find Piero with Astella. Piero tells his master that he has fulfilled his command, and expects reward; Lodwick tries to kill him, forcing Piero to admit that Astella has not submitted to him. The chastened and reformed Lodwick decides to renew his vows with Astella, making them a third matrimonial couple at the play's end. Lodwick also demands punishment for the "libertine" Grimuldo – but the devil-woman turns out to have been Grimuldo's wife Belinda; the ruse is exposed.
Comic relief is provided by Jacomo, Cleona's steward; ambitious but foolish, he resembles Malvolio in Shakespeare's Twelfth Night.[4] The plot device of a courtier trying to get another man to sleep with his wife so he can divorce her is re-used by Shirley in his next play, The Humorous Courtier.