Gosford Park was written by Julian Fellowes who also wrote Downton Abbey, and they both share a similar setting. Downton Abbey was originally suppose to be a spin-off of Gosford Park but the idea eventually morphed into something else with characters not related to those in the Gosford Park film
Like the Crawleys of Downton Abbey, the story of this film is about the aristocrat William McCordle, his family, and their friends. They live in a large mansion in the countryside of the United Kingdom. They have a lot of guests arrive, most of whom came to go hunting the next day. Most of the guests also bring their personal servants who help the household servants with daily matters of keeping their lords and ladies happy.
Matters for the aristocrats upstairs tend to be a lot of secrets and unhappiness. Especially when it comes to anything William McCordle is concerned with. The servants downstairs typically gossip about what happens. Especially as one of the guests is a Hollywood producer, and another is a famous actor. However the house suffers a big tragedy, and a giant mystery is out there to be solved of who did it.
I will say that Downton Abbey fans typically will not suffer deja vu watching Gosford Park. You could imagine the Crawley’s being invited to a house party with the McCordles, but the stories and characters are much different. Maggie Smith is also in the movie, but her character is a little similar but nothing quite like the Dowager Countess of Grantham, Violet Crawley. I enjoyed the movie quite a bit, though the first half of the movie just moves too slow. Though I did like the revelation near the end.