A long feud between two Spartan families has ended with the loving engagement of their children, Penthea and Orgilus. Penthea’s father, however, dies before the wedding can take place, and her twin brother, Ithocles, forces her into a socially advantageous match with a ridiculously jealous older man. Ithocles returns to Sparta a war hero and falls in love with the Princess Calantha, hoping for precisely the joy he has deprived his sister. When Origlus takes his revenge, Calantha cannot stand aloof.