Phaedra opens with Hippolytus, son of Theseus and stepson of Phaedra, setting off on a hunt. He prefers the woods to the palace, and invokes Diana, goddess of the hunt, to help his luck. After his departure, Phaedra appears, racked with despair. Her wet-nurse inquires what it is that ails her; Phaedra confesses that she is in love with Hippolytus, and recalls her own mother Pasiphae’s lust for a bull – a lust that gave birth to the infamous Minotaur, which Theseus himself slew. She claims she is cursed by Venus, who is angry against Apollo, Phaedra’s ancestor, for having exposed Venus’ love for Mars.
The nurse pleads to Phaedra to control her passion and check her emotions, but it is no use. Phaedra speaks of herself as though of a ship caught in a storm and heading for the rocks: try as she may to change course, the waves will inexorably pull her toward her doom. Realizing the hopelessness of the situation, the nurse resolves to try to help her mistress.
Hippolytus, biological son of the Amazonian Antiope (former wife of Theseus) is known to detest all women and forsake the pleasures of civilization. When he returns from the hunt, the nurse attempts to soften his heart, arguing that he should make use of his good fortune and enjoy fine food, wine, and the company of women. Hippolytus roundly rejects the idea, proclaiming that nature is where man is at his most free and innocent and that womankind is the cause of much evil.
At that moment, Phaedra appears, and swiftly collapses in a swoon. Hippolytus wakes her, then asks why she is so ill at ease. Unsure how to proceed at first, Phaedra summons the courage to tell Hippolytus the truth, hoping he may reciprocate her feelings and lend her “success” to cover up her “sins.” As it turns out, however, Hippolytus flies into a rage, railing against Phaedra and declaring her worse than her “monster-bearing mother.” He draws his sword on her, but when she says she hopes to die, he casts the weapon away and flees into the woods.
Phaedra’s nurse hatches a plan to conceal Phaedra’s guilt by accusing Hippolytus of attempting to rape his stepmother. His abandoned sword will serve as evidence. Shortly thereafter, Theseus returns, freshly escaped from the underworld. He sees Phaedra in distress, seemingly prepared to kill herself, and demands an explanation. Phaedra tells him someone he would least expect tried to rape her; she then points to Hippolytus’ sword. Theseus is aghast, and immediately calls on his father Neptune to kill his son.
A Messenger arrives, bearing news of Hippolytus’ death. As we learn, a monster emerged from the windswept sea and pursued Hippolytus’ horses; caught up in the reins, the young man was dragged and torn limb from limb. Seeing Hippolytus’ mangled corpse, Phaedra confesses the truth to Theseus, then falls on her sword and dies. Theseus curses himself for his foolhardy decision, then orders Hippolytus’ remains be gathered for a proper burial. “As for her,” he says, turning to Phaedra’s body, “let her be buried deep in earth, and heavy may the soil lie on her unholy head!”