It’s The Railway Children.
The scene at the end, where Bobbie is waiting on the station platform, and a train arrives, and all the passengers get off. The very last person to get off the train is… Bobbie’s father! Who had been wrongly imprisoned as a spy, but has at last been vindicated and released.
It always makes me cry.
You can’t watch the whole film, but you can read the whole book on Project Gutenberg.