Zola's 1890 novel has been much filmed but the only memorable version was made by Jean Renoir in 1938; this greatly simplifies the plot and updates it to the 1930s. Jean Gabin plays the engine-driver Lantier, and it was said that Old Stoneface and his fireman spent much time rehearsing on a real engine so that the footplate scenes would carry conviction, which they certainly do.
It's not the all-time great film that the corny trailer says it is, but it's a thumping good melodrama. Lantier has a strange quirk which causes him to become homicidal at times of stress, or through frustration. He tries to sublimate his desires by being passionate about locomotives, as so many of us did when very young, but this doesn't really work; he becomes enmeshed in some splendidly sordid murders and finally kills himself by jumping out of the cab as the train speeds towards Paris. The fireman stops it and sadly walks back to find the body.
Zola's ending to the story is rather different. The train is carrying troops towards the front at the outbreak of the Franco-Prussian War, and a fight between Lantier and his fireman breaks out; both fall to their deaths as the train full of happy, drunken, doomed soldiers hurtles driverless through the night.
There is one sequence which I could watch over and over again. They are holding a Railwayman's Ball, and there is much jollity in the dance hall while Lantier is strangling his mistress Séverine (Simone Simon) elsewhere. The scene cuts between the murder and the dance hall, where an orchestra is playing a waltz accompanying a man who is singing, beautifully, a song I have loved for years. His name was Marcel Veyran, but although he was a well-known actor/singer he was uncredited in the film and I could not find a recording. However, to my huge delight I have just found the tune—Le P'tit Coeur de Ninon—on the net, being sung in much the same style by Réda Caire.