Lillesang - The secret of the dark mermaid

When Jo and her family inherit the old house on the Danish coast, odd neighbour Bente tells the story of the gongur that comes ashore and draws people into the sea. Unlike her mother, who avoids the water, Jo doesn't let the old woman chase her into the Bockshorn. At night, however, she is actually lured to the beach by a voice. Bente can save the sleepwalking girl at the last minute. What is it about the mermaid creature? And why does Jo's mother hide old photos with faces scratched out?