The movie opens with a man in a mental hospital speaking to his doctor. He is suffering survivor's guilt due to a rock climbing incident where he chose to save himself and let his friends die by cutting a failing line. He is chastised by his doctor, who tells him that the average person would have chosen to die with his friends.
The scene changes to seven college kids celebrating their upcoming graduation in a secluded house 50 miles from civilization. It's supposed to be a weekend of sex, booze, and partying. The fun comes to and end when they receive a video, showing two of the group, Carlos and Nicole, kidnapped. On the tape, Nicole is given a gun and told to kill Carlos to save herself. She can't, and turns the gun on the assailant, who overpowers her. Carlos is then thrown into a pit and injured. The tape tells the other five that they have a choice: kill their friends to save themselves or be killed. They have until 6:00 AM the next day. If one person is alive, that person goes free. If more than one are alive, they will all die.
Carlos is returned to the house, where he and the other five decide to escape by driving away. The killer tells them that he has wired their van, and have 60 seconds to throw someone out or they will all burn to death. Carlos is thrown from the van, and is then shot and killed. The remaining students then turn on each other, and start killing each other off. It ends with last two, Michael and Amber, nearly lasting till 6:00. Michael, who was stabbed earlier by Jennifer, finishes himself off in order to leave Amber as the lone survivor.
The twist is that the killer is the patient from the beginning of the movie and Brent, one of the students, is the doctor’s son. The killer staged the event to prove his point and he used his doctor's son to help prove it.