Returning home from the Trojan Wars during a storm, Idomeneo, the king of Crete, vows to sacrifice to Neptune (the Greek god Poseidon) the first living creature he meets ashore in return for his own safety. The first person he sees turns out to be his own son Idamante, and Idomeneo attempts to escape from fulfilling his vow. Idamante, meanwhile, is loved by orphaned prisoner Ilia and by the jealous Electra. Who will be sacrificed, and who will stay with Idamante?