In 'House on the Marsh,' an 18-year-old governess named Violet Christie arrives at an isolated mansion in the Norfolk countryside. Despite her initial enthusiasm, she soon begins to uncover a web of mysteries and secrets surrounding the family she serves. The aloof mistress of the house, the enigmatic Mr. Rayner, and the haunting warnings from the villagers all hint at a sinister past. As Violet delves deeper into the hidden truths, she finds herself entangled in a dangerous game of deception and intrigue.