I've had a great idea for a low budget Brit-flick film thing:-
A group of strangers find themselves together in some kind of situation, I dunno, shipwrecked on a desert island, or stuck in a lift, or kidnapped by a genius psychopath, and after trying to figure out why they are there, they come to the conclusion that the thing that connects them is some shadowy person from their past, a mutual acquaintance, someone used to live with them, sold them a car, went to school with them, picked them up hitchhiking, whatever, this one person that they all know.
Then it turns out that he's got nothing to do with their predicament, and its just coincidence, like six degrees of separation, and after pinning all their hopes that its cos of this guy, they end up dead. Whatever mechanism or person that brought them together and killed them is just a little puzzled by their unexpected connection, but doesn't let it interfere with the sick but otherwise quite banal plan.
Later the shadowy bloke from their past reads about their deaths in the newspaper, gets a little freaked out that these disparate people who he knew all died together, but then otherwise just carries on with his day.
Life goes on.