Six best friends from college have their own secret graduation party, but the group's stoner orders a hallucinogenic from her drug dealer, who lingers around to join in the fun. The ladies' wonderful night gradually devolves into a dark, hazy nightmare of blood and violence as they are drugged and bewildered. Five years later, the sisters reunite in a cabin in the woods in the aim of rekindling their tight friendship, only to discover that they are being stalked by someone or something they do not recognize...