A Spanish nobleman named Piraquo was banished from Spain in his youth; after a very profitable career as a pirate and a stay at the royal court of Portugal, his banishment has been lifted by Don Carlo, the heir to the Spanish throne. Piraquo's son Don Manuel is a close friend to Don Carlo, and returns to Spain with his father. Don Manuel quickly falls in love with Clara, the daughter of Duke Mendoza. Clara loves him in return and agrees to marry him – but the Spanish princess, Maria, also falls for Manuel, even though she is betrothed to marry Prince Antonio of Portugal. Don Carlo is also engaged to a Portuguese princess, Isabella – though Carlo too is in love with Clara.