 When detective Eric Matthews (Donnie Wahlberg) is called to a crime scene of a victim of Jigsaw (Tobin Bell), he finds a lead to the place where he is hidden. Once there, he realizes that Jigsaw trapped his son Daniel Matthews (Erik Knudsen) with three women and four men in a shelter, and they are inhaling a lethal nerve gas. If they do not use an antidote within two hours, they will die. Eric follows with increasing desperation the death of each member of the group in monitors, while trying to convince Jigsaw to release his son.