After being left in the bathroom to die, Detective Eric Matthews breaks his foot with a toilet lid to escape his shackle.
Six months later, the aftermath of a Jigsaw “game” is discovered by a SWAT team. The victim was meant to rip chains from his body in order to escape from a bomb. Detective Allison Kerry arrives at the scene, and points out that the room’s exit was welded shut, breaking Jigsaw’s modus operandi of giving his victims a chance to survive. While reviewing the videotape, she is abducted and awakens in a harness hooked into her ribs. Kerry manages to retrieve the key and unlock it before the timer expires, but it kills her anyway.
Dr. Lynn Denlon is abducted from the hospital where she works, and brought to the bedridden John Kramer. His apprentice, Amanda, locks a collar around Lynn’s neck that is connected to John’s heart rate monitor and will detonate if John dies or Lynn moves out of range. She is instructed by Amanda to keep him alive until another victim has completed his game. The other victim Jeff, wakes up in a box and learns that he must undergo tests which will lead him to the man who killed his son Dylan in a drunk driving accident. Jeff became unstable and vengeful as a result, and now neglects his daughter.
Jeff’s first test leads him into a meat freezer. He finds Danica Scott, the only witness of Dylan’s death, who refused to testify in court; she is chained at the wrists between two poles which begin spraying her with ice-cold water. Danica manages to convince Jeff to help her, but freezes to death before he can retrieve the key.
His second test leads him to a vat, at the bottom of which Judge Halden, who gave Dylan’s killer six months in jail, is chained at the neck. Large pigs drop into a liquidizer and spray Halden, but Jeff sets fire to a cage full of Dylan’s toys in order to retrieve the key and saves Halden before he drowns. His third test involves Timothy Young, Dylan’s killer, who is strapped to a machine that will twist his limbs and neck until they break. The key is tied to the trigger of an enclosed shotgun. Jeff accidentally kills Halden when he takes the key, and is unable to stop the machine before Timothy’s neck breaks.