The film is set on the eve of WWII in a Yorkshire mining town. After falling on hard times, the Carraclough family is forced to sell Lassie, their beloved dog, to the Duke of Rudling. When Lassie finds herself transported five hundred miles away to live in the Duke's remote castle on the northern coast of Scotland, she is determined to defy the odds and return to her home. So begins an incredible adventure, set against a stunning series of British landscapes, that sees Lassie facing dangers natural and human and finding help in unexpected places as she makes her way across the country, to reach home in time for Christmas.