Shenxiu was abandoned by her mother when she was a child. Since then, she’s had bad dreams about a monster called Nightmare. One day, she travels on a cruise ship with her family. On a stormy night, she sees Nightmare on the deck, humming her mother’s song and calling her to the sea. She falls and breaks into the fancy Deep Sea restaurant, in an old transformed submarine. She meets the Chef, Nanhe, and embarks on a mysterious journey.