sentences:  Cassander expects the Queen to announce her choice of Lisimachus as her consort; he, and the court in general, are astounded when she chooses Arcadius instead.Macarius and the local Bishop intervene before the ceremony can occur; they reveal that Arcadius is actually Demetrius, a royal prince missing and assumed dead — and therefore the Queen's long-lost brother.It transpires that Theodosius, the prior king and the Queen's father, had hidden his two young sons, Leonatus and Demetrius, through a fear that Cassander would usurp the throne and kill the princes after Theodosius's death.