An ancient Breton legend tells of Ys, the richest and most powerful city in Brittany, which was swallowed up by the sea as a punishment by God for its adherence to the old Celtic deities. King Gradlon was given the chance to escape if he threw his beloved daughter Dahut into the sea. The cathedral bells are said to toll beneath the waves to warn of storms, and to mourn the souls of the children of Ys. Inspired by this legend, Retrospect's programme interweaves Breton lais, medieval ballads, 16th-century airs de cours, plainsong and traditional songs of the sea.