Charleston, South Carolina. Socialite Desiree "Des" Cartier (Taylor Cole) is hosting a debutante party at her mansion on the evening of April 1, 2007, for her best friend and aspiring actress Torrance Caldwell (Scout Taylor-Compton). Present for a pre-festivities toast are Taylor's brother Blaine Cartier (Josh Henderson), who controls their joint inheritance from their late parents (to Desiree's dislike); U.S. Senate candidate Peter Welling (Samuel Child), Peter's "Miss Carolina" fiancee Barbie Reynolds (Jennifer Siebel), and the quintet's less wealthy videographer friend Ryan (Joe Egender). With the party in full swing, Desiree's social nemesis and Ryan's not-so-secret crush Milan Hastings (Sabrina Ann Aldridge) arrives for her 21st birthday which is on that very day. Also present is the chihuahua-toting society reporter Charles (Joseph McKelheer).
As another in her long string of April Fool's pranks, Desiree suggests Blaine get Milan tipsy on champagne and pork her in his bedroom upstairs. Desiree and several of the others hover by the cracked-open bedroom door, prepared to videotape the affair with the camera Desiree lifted from Ryan. However, Milan's drink was spiked with a "roofie," so she stumbles into the hallway in her lingerie and tumbles backwards over the railing to her death 20 feet below.
A few days later, an inquest-probate judge decides not to press criminal charges against Blaine and rules Milan's death as an accident. But due to Blaine's growing history of woman trouble, turns over control of the family fortune to Desiree (and she's able to buy her annual red Mercedes, upon which Blaine had been hesitating before the household tragedy).
One year later. Desiree, Blaine, Peter, Barbie, Torrance, and Ryan receive anonymous invitations to meet on Milan's grave at noon, April 1, 2008, with the cryptic P.S. "I have proof." Just after the entire sextet is back together, a messenger comes to the grave with a box containing a letter and a lap-top computer. The letter says that one of the six murdered Milan, and if that person does not confess, all of them will be dead by midnight. As a show of intent, the computer has footage of Charles drowning in his pool.
Everyone leaves the cemetery and goes to the pool to confirm this mishap. Subsequently, an increasingly frantic Desiree sees one "suspect" after another "murdered" before her eyes (though the bodies keep disappearing). Barbie is electrocuted in a beauty pageant dressing room, Peter's campaign truck runs him down in a parking garage, Ryan's throat is slit in his humble apartment, and returning home, Desiree and Blaine discover even their long-time butler Wilford (Frank Aard) has been butchered in the kitchen.
After a brief separation from her brother, Desiree finds him tied to a chair. Worse yet, the gun-wielding Torrance soon has Desiree tied up inches away in another chair. After some back and forth, and Torrance fatally shooting Blaine in the chest, a chagrined Desiree finally admits it was SHE who spiked Milan's fatal drink, while allowing her brother Blaine to become the "fall guy." At this point Blaine cannot contain a chuckle, and soon the whole crew of 2008 "victims" are surrounding a still-tied Desiree, telling her what a bitch she is, and how they have conspired to prove it to her. (Milan continues to be dead and buried, of course.) Special effects people from Torrance's latest movie, BOOGIE NIGHTS 2 set have equipped Blaine and the others with "squibs," and other cast members faked Desiree out by dressing as cops and "confirming" Ryan's murder as she and her brother were fleeing the scene.
To illustrate her end of the charade involving a revolver shooting blanks, Torrance pulls the trigger once more. Unfortunately for Desiree, this time the cartridge in the chamber is real, and the bullet blows off the top of her head, killing her for real.
The next scene involves the same inquest-probate judge from a year earlier absolving Torrance of any guilt for Desiree's death, and confirming Blaine as sole heir of the family estate. The final scene shows Blaine driving off in what was Desiree's red Mercedes, a slowly building smirk on his face... (implying to the viewers that he intentinally placed a live round in the gun knowing Torrance would 'shoot' Desiree and thus with her gone, he now has all of the family wealth for himself).
During closing credits, a snippet paralleling an earlier scene is inset next to the cast and crew listing, as Charles tells an entertainment show anchor how it feels to have his own TV show, largely thanks to the books he's written on the two socialite killings.