When their father is sent away to prison, three London children move to the country where they keep busy preventing accidents on the nearby railway, making many new friends, and generally learning a good deal about themselves

A mother and her three Edwardian children move to a country house in Yorkshire after the mysterious disappearance of their father. The children become fascinated by a nearby train and their kindness helps them befriend an older gentleman who may be able to solve the mystery of their missing father