A bachelor party weekend in the great outdoors takes some unexpected detours.

Ken Andrews (Faison) has been the orchestrator of the hazing pranks at all of his buddies' stags - elaborate, hilarious pranks that have left many emotional scars and a few physical ones. And now today is Ken's stag! He nervously awaits the fate that his pals surely have in store for him, comforted only by the knowledge that Carl (Pat Thornton) will be there to watch his back. That is, so long as Carl can extract himself from the Hollywood celebrity, Veronica (Amurri). Ken will soon discover that payback is worse than he could ever imagine.

In Las Vegas, the powerful three hundred year old vampire Sylvian hires Dr. van Helm to research a cure to survive in the sun. She uses three vampire women as guinea pigs to test the serum in the desert and a couple that is camping witnesses the failure and calls the police. Detective Stanton and his partner Detective O'Hara are assigned to investigate the case. Meanwhile, Jason, who is going to marry Rachel, and two friends travel to Las Vegas for his bachelor party with a couple of strippers, but the women are actually vampires that attack them. Out of the blue, Rachel and her friend Nikki decide to travel to Las Vegas to surprise her boyfriends. The group is captured by Sylvian that uses them to feed the pack vampires and test the new research.

When he wakes up the morning after his bachelor party in bed with a strange woman, a man presumes he must have cheated on his fiancée. Guilt leads him to try to cover it up in the week before the wedding, high jinks ensue.