The story describes a magical underwater city where people called Osiers live. The Osiers were originally living on land but used magic to move their city underwater when humans interfered with their lives. The story is told to some children by their grandfather, who reveals he is actually from the underwater city himself. He tells them stories of breathing underwater, riding sea animals, and meeting sea creatures. The children want to visit the magical place. In the end, it is revealed the grandfather was just dreaming about the underwater city and telling the children about it in his sleep.