A group of friends stop to pick up a hitchhiking woman only to end up getting drugged by her with a gas. They awaken to find that vials have been implanted in the base of their skulls. They are, of course, instantly fatal if removed. A grinning, professional-looking woman informs them on TV screens that they have 22 hours to fill these vials with a specific amount of brain fluid - a fluid that is produced during times of extreme pain. Along with another group of unlucky test subjects and with time ticking away, they decide to work together and share the burden of reaching their painful target.