The Birthday Party 2003

It's Tiffany's twenty-first birthday, and she's having a party with her closest friends. There's lots of drinking and kissing, and as the party progresses, various couples pair off, including Tiffany's boyfriend Drew with someone else. Her closest friend, Beth, hears strange noises from time to time, and finally goes to investigate. Tiffany and Drew follow with a flashlight. What sort of party will this turn out to be, and will Tiffany find true love?