In this particular slice of the subgenre, said group consists of a bunch of friends who stop to pick up a hitchhiking MILF and find themselves summarily drugged. Awakening with vials implanted in the base of their skulls (which of course are instantly fatal if removed), a grinning professional type informs them via TV screens that they have a certain length of time to fill these vials with a specific amount of brain fluid. Fluid that is most easily produced during bouts of extreme pain. You can see where this is going already, can't you? Along with another band of unlucky subjects, they all get together to bring the pain to each other and share the burden of reaching their target.