The Legend of Tsar Saltan: Dresden State Opera (Siegfried Kurz) (1978)

Fantasy about a fictitious Russian Tsar who weds the youngest girl, Militrissa, out of three sisters and while he's away on a military campaign she gives birth to a Prince. Her two envious sisters tell the Tsar that Militrissa has given birth to a monster and he orders them to be executed. She escapes with her infant, Prince Guidon, to a desert island where he matures and becomes a hero after saving a swan. Through the swan's magical powers Guidon surreptitiously gets into the Tsar's palace in search of his real identify. When the swan turns into a princess, Guidon falls in love with her; the Tsar accepts them both and Militrissa forgives everyone.