The story goes like this: on his return from winning the Trojan war, the king of Crete, Idomeneo gets caught at sea in a storm. Neptune, God of the oceans, lets him go home safely only after Idomeneo vows to sacrifice the first person he meets on land. Of course, the Gods being a facetious bunch, it's his son Idamante who happens to be there. Idomeneo and his legal councel wise advisor Arbace decide to send Idamante away rather than fulfill the pledge. Neptune is not amused, and sends some Godzilla monster to Crete. Idamante goes and kills the monster, an act of courage which earns Neptune's admiration and forgiveness.
Pictures courtesy of SF Opera, by Terrence McCarthy. Genia Kühmeier, Kurt Streit, and Alice Coote from top to bottom.