Photographer Andy Schroeder (Jared Leto) and oncologist Lucas Gardner (Aaron Eckhart) regain consciousness while chained to pipes at either end of a filthy bathroom. As the two men realize they've been trapped by a sadistic serial killer nicknamed "Jigsaw" and must complete his perverse puzzle to live, flashbacks relate the fates of his previous victims. Meanwhile, Dr. Gardner's wife (Heather Graham) and young daughter (Britt Robertson) are forced to watch his torture via closed-circuit video.