A village cricket team plays its last match before most of its players go off to fight in World War I, confident that "it will all be over by Christmas".

At the dawn of the 20th century, following their father's arrest on suspicion of betraying state secrets, the three Waterbury children—Bobbie, Phyllis and Peter—move with their mother to Yorkshire, where they find themselves involved in unexpected dramas along the railway by their new home. This stage-to-screen version, filmed at the National Railway Museum, features the steam train from the much-loved original feature film.

A Yorkshire coal mine is threatened with closure and the only hope is for the men to enter their Grimley Colliery Brass Band into a national competition. They believe they have no hope until Gloria appears carrying her Flugelhorn. At first mocked for being a woman, she soon becomes the only chance for the band to win.