What unfolds is a story based around an incoming 'gas' which everyone knows about and for which the government has issued suicide pills because there's nothing anyone can do about it - and those who don't take the pill will suffer a fate worse than death in great pain. So they have one last night to party before they all snuff themselves out as they know the exact day it is arriving.
It plays out in the early stages (as the group arrive at the big countryside house) a bit like Peter's Friends or even Four Weddings. All frightfully chirpy, hilarious fun with much posh-people banter. They have dinner. They argue. Truths come out about the past, secrets shared, anger expressed, beans spilled. Think Abs Fabs, air-kisses, Land-rovers and Barbour jackets too. The monied-set.
Seems that posh kids are allowed to swear as much as they like and use the F word in pretty much any sentence (along with their parents) as the four kids are a bunch of just-as-annoying public school posh-brats in the mix. They're all very unlikeable and actually, none of the characters are really developed very much in the 90 minute run-time.
Keira Knightley leads them - a (mainly) Brit-pack of actors including Matthew Goode, Roman Griffin Davis, Annabelle Wallis, Lily-Rose Depp, Sope Dirisu, Kirby Howell-Baptiste, Lucy Punch, Rufus Jones and Davida McKenzie. It's a bit like spot the face you know, then work out which TV series or film you saw them in! They all do what they do reasonably well and if 'convincingly annoying' is the aim, then they're all cracking actors!
Anyway, I won't spoil the ending (which you will see coming from some way off) but leave you to either get very annoyed by the people and what they represent in life or see past that and enjoy the dark side of what starts as an apparent comedy but ends up as something quite different.
Most of it shot in the house and is generally directed and staged well - it could easily be a stage-play. Perhaps it is. Now available to rent/stream from various services.