The first difference was that in the film, the young man worked for the old man. In the film, the old man was also mean too. The old man was so rude to the younger man that it was the reason the young man went “mad”.
Another Difference is that in the book, the whole story took place over 8 days. In the film, everything happened in one day. The effect it had was that the old man was surprised but not as surprised as he was in the book. I think that because in the book the young man