Hilda, a lonely girl who lives by the coast and loves mermaids, encounters a mermaid who has been blown ashore by a storm. Hilda welcomes the mermaid into her cottage, and the mermaid describes her life in Neptune's underwater kingdom. As they sleep, the mermaid disappears. Hilda remembers her encounter, finding seaweed on the floor and looking for the mermaid whenever she is on her boat.