The story follows the adventures of the Waterbury children, who are forced to move with their mother (Dinah Sheridan) from a luxurious Edwardian villa in the London suburbs to "Three Chimneys", a house near the fictional 'Great Northern and Southern Railway' in the Yorkshire dales, as the father (Iain Cuthbertson), who works at the Foreign office, has been imprisoned as a result of being falsely accused of selling state secrets to the Russians.
The three children, Roberta (Bobbie) (Jenny Agutter), Phyllis (Sally Thomsett) and Peter (Gary Warren), find amusement in watching the trains on the nearby railway line and waving to the passengers. They become friendly with Albert Perks (Bernard Cribbins), the station porter, and with the Old Gentleman who regularly takes the 9:15 down train. Meanwhile, to earn money to survive during her husband's absence, Mother writes and sells stories to magazines.
After many adventures, including saving the lives of dozens of passengers by alerting a train to a landslide, rescuing a Russian dissident, Mr. Szczepansky, and uniting him with his family, and caring for Jim, the grandson of the Old Gentleman, who is injured whilst participating in a paper chase, Bobbie eventually discovers the truth of her father's absence and appeals to the Old Gentleman for his help. He is eventually able to help prove their father's innocence, and the family is reunited.
This is regarded as one of the greatest children's films of all time. :) xx