The Big Swap is a 1998 British

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

drama film discussing the exchanging sexual partners for one night. As the name of the movie indicates it discusses the "swapping" or "swinging" between bunch of friends and how it affects their lives.

Plot

A group of friends meet and plan to swap partners for one night. Every man brings his car key and they all throw it in a bunch of bowl and mix it up. Then the women picks up blindfolded one of the car keys and has to spend a night with whoever's owner of that car key. It's all fun and games at first, but after the party they all begin to regret their choices and the direction of their lives.