12 in a Box (2007)

At a school reunion dinner in a remote country mansion, a dozen people are offered the chance to collect a million pounds each if they can stay on the estate, cut off from the outside world, for 96 hours. With deaths, sexual intrigue, kidnapping, and spiraling levels of farce and confusion, the action barely pauses for breath as it heads towards its "Will they or won't they succeed" climax.