The king of Calabria has usurped the crown of Sicily from Prince Philaster’s father, now dead. Because the Sicilian people love their young prince, however, the king does not dare imprison him or harm him in any way, but he does plan to marry his daughter, Arethusa, to Pharamond, a Spanish prince, who would thereby become heir to both thrones. Pharamond proves to be pompous and conceited. When Philaster, who is quite free and outspoken in his manners, tells Pharamond that only over his dead body could he marry Arethusa, the king admonishes Philaster to restrain himself. Philaster declares that he will restrain himself only when he is better treated; he believes that he is suddenly possessed by the spirit of his late father. Philaster is promised aid by the loyal Lord Dion and by two noble gentlemen, Cleremont and Thrasilene.

At an audience with Princess Arethusa, Philaster is taken aback when he hears Arethusa tell him that she loves him deeply, and he declares his love for her in return. To avoid detection under the suspicious eyes of the court, he promises to send his servant to Arethusa as their messenger. When Pharamond enters Arethusa’s apartment, Philaster departs with words of scorn for the boastful Spanish prince. Later, he has difficulty in persuading his servant, Bellario—who is actually Lord Dion’s daughter, Euphrasia, in disguise—to enter Arethusa’s service.

At court, meanwhile, Pharamond attempts the virtue of Galathea, a court lady who leads him on but refuses all his base suggestions. Later, he makes an assignation with Megra, a court lady of easy virtue. Galathea, having overheard the conversation between Pharamond and Megra, reports the prince’s dissolute ways to Arethusa.

That night the king discovers Megra in the prince’s apartment. Pharamond is in disgrace. Megra, however, manages to extricate herself to some extent by insinuating that Arethusa is as wicked as she and that Bellario is more than a mere servant to Arethusa. The princess makes much of Bellario because the page is a gift from Philaster. The king, who has not even heard of Bellario’s existence, is confounded by Megra’s suggestions.

Megra’s story convinces even Philaster’s friends that Arethusa is unfaithful to the prince, but when they tell Philaster what has happened he refuses to believe them. Nevertheless, his trust in Arethusa is shaken. When Bellario delivers a letter from Arethusa to Philaster, who is still in doubt, the disguised girl innocently damns herself by speaking in praise of Arethusa and by describing Arethusa’s virtuous affection for the page. Philaster accuses Bellario of perfidy and, overcome with the passion of jealousy, threatens to take the page’s life. Only because of Bellario’s sincere protestations of innocence does Philaster, although still not convinced, spare his servant.

The king orders Arethusa to discharge her young page. When Philaster finds Arethusa depressed over Bellario’s dismissal, he reveals his suspicions and declares that he will give up his claim to the throne and become a hermit. The wretched Arethusa, knowing that she is guiltless, can do nothing to prevent Philaster’s departure.

Philaster goes to a nearby forest and wanders about disconsolately. At the same time the king and the court enter the forest to hunt. During the chase, Arethusa disappears. The hunters find her riderless horse but no trace of the princess. Bellario, having been banished from court, also went into the forest. When he encounters Philaster, the page is brusquely ordered away. In another part of the forest, Arethusa, stunned by recent events and without direction in her wandering, sits down to rest and suddenly faints. Bellario appears in time to revive her, only...