When a financial crisis hits the Carraclough family, they are forced to sell their beloved dog to a local duke, but Lassie isn't happy with her new living arrangements and soon sets out on an 800km journey back to the home she loves.
When a family leaves an urban sprawl to start their lives over again in rural Montana, and when a devious neighbour plots to steal their farm out from under them, Lassie comes to the rescue.