In 1852, the famine on a desolate Britanny's island named Blaz-Mor, off the coast of Finistère. Some residents exalted hold responsible the young Moira (Renée Cosima), equivalent to a witch. The old Marnez (Charles Vanel), "head" of the island, is trying to restore calm and opposes Yann Le Heart (Henri Vidal), the fiancé of his daughter Louise Kermelen (Dany Carrel), who wants causing a shipwreck to save the island from famine.
