The Coronation is a Caroline era stage play, a tragicomedy written by James Shirley, and notable for the tug-of-war of authorship claims in which it was involved in the middle seventeenth century.
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.
When the Queen is suddenly removed from power and her wedding cancelled, she suspects that Polidora is Lisimachus's new love, which generates a subplot of romantic cross-purposes, jealousies and misunderstandings.
Cassander, in a rage at the disruption of his well-laid plans, devises a plot to regain power: he intends to advance Seleucus as the elder missing prince, Leonatus, and so eject Arcadius/Demetrius from the throne.
The intended coup d'état is mounted, only to encounter another twist of fate — Eubulus and the Bishop reveal that Seleucus actually is the missing Leonatus, and thus the true king of Epire.
In the play's climax, Cassander is forgiven his treachery if he vows allegiance to the new monarch, and Leonatus achieves his rightful place as king; and the couples Demetrius and Polidora, and Sophia and Lisimachus, have their misunderstandings resolved and are happily united once again.