Murder mystery set at 1920s English garden/weekend party

This was a one shot mystery novel that dealt with a murder that is committed at a garden party or weekend party in the early 1920s. Unfortunately, I don't remember much more than that about the plot, but I do remember that it's been included lately in all the displays of Downton Abbey-themed books that one can find at bookstores. I also remember that it had a greenish cover - possibly with a picture of a couple of people sitting down at a table outside. It was trade paperback-sized. Thank you!

Maybe The Shooting Party by Isabel Colegate

Kate Morton had one set in that time period with sisters. The Fogotten Garden

A Fete Worse Than Death by Dolores Gordon-Smith is the right sort of topic, time period and colour - although it's part of a series since it's the first one, it might not have been badged as such?

I don't think it's any of those books. I've heard of The Shooting Party and Kate Morton's books, but I'm fairly certain those aren't the book the I'm thinking of. I've read A Fete Worse Than Death, and a couple from that series, and I can't recommend them enough (fun books), but I know for certain I'm not thinking of those. Thank all of you for your help :)

It certainly sounds like The Shooting Party...

I found it! I was wandering around in a used bookstore and the cover caught my eye. The book is Death in the Garden by Elizabeth Ironside. I haven't started it yet, but it looks very interesting.

Fantastic! Thanks for coming back to let us know!

And Ironside is good!