Manfred is the Prince of Otranto, but a mysterious prophesy suggests that he may not be so much longer. He is not well liked and the legitimacy of his rule is in question. He wishes to secure his power by marrying his son to Isabella, the assumed closest descendant of Prince Alfonso, the beloved original Prince of Otranto. Suddenly, a giant supernatural helmet appears and crushes Manfred’s son to death. The blame is publicly pinned on a stranger Manfred accuses of witchcraft, but personally, Manfred fears the prophesy is coming true and he rushes to enact plan B: divorce his wife and marry Isabella himself. Then Isabella’s hitherto presumed dead father appears at the castle and, spurred on by a reanimated skeleton sent from God, forbids the alliance. Then the giant helmet joins giant armor and kicks down a large part of the castle, proclaiming that the accused peasant is the lawful prince — who, it turns out, was the long-lost grandson of Alfonso.