Presented by David Mitchell in a coastal village in medieval Japan, a small boy named Isako battles to keep his family alive against odds. With his father's departure, Isaku is forced to grow well before his time.

He must learn how to fish, how to distribute salt, and about all the vast secrets of the sea, not least the myth of "Fu-Sama", the destroyer of sea vessels, which provides the village with an unexpected reward. When the ship's founders rejoice on the rocks, Isako and the villagers are happy.

Long ago they arrived for sea gifts. But the goods are not at all the pool they were hoping for.

At first it is puzzling, and then terrifying, there is something dark coming to the beach, and it is about to change their lives forever.