Saw IV is a 2007 horror film directed by Darren Lynn Bousman from a screenplay by Patrick Melton and Marcus Dunstan, and a story by Melton, Dunstan, and Thomas Fenton. It is the fourth installment in the Saw film series, the third directed by Bousman. The film stars Tobin Bell, Scott Patterson, Costas Mandylor, Betsy Russell, and Lyriq Bent. Set concurrently with the events of Saw III, the plot follows Daniel Rigg, a police officer obsessed with rescuing the Jigsaw Killer's victims, who finds himself the focus of Jigsaw's latest series of tests, in which he must rescue his partners, Eric Matthews and Mark Hoffman, while learning to overcome his obsession. The film also explores John Kramer's legacy and his ability to manipulate people into continuing his work after his death, while providing more of his backstory and an additional explanation as to why he became Jigsaw.
Saw IV was the first film in the franchise to not be written by Leigh Whannell. It was released by Lionsgate in the United States on October 26, 2007, and received generally negative reviews from critics. Despite this, the film was a box office success, grossing $139 million worldwide. A sequel, titled Saw V, was released in 2008.
A wax-covered microcassette is found in John Kramer's stomach during his autopsy, which contains a posthumous message from John that informs Detective Mark Hoffman that he will be tested. Elsewhere, two men – one with his eyes sewn shut, the other with his mouth sewn shut – awaken in a mausoleum, chained at the neck to a winch that begins reeling them in. The muted man is forced to kill the blinded man to get a key from his collar and free himself.
Following Detective Allison Kerry's death in a "Jigsaw game" set up by Amanda, a SWAT team led by Hoffman and Officer Daniel Rigg and Kerry's FBI contacts Peter Strahm and Lindsey Perez arrive at the crime scene. Noting the physical limitations of John and his apprentice, Amanda Young, Strahm speculates that a third accomplice was involved and becomes suspicious of Rigg. That night, Rigg, who has become obsessed with rescuing Jigsaw's victims since Detective Eric Matthews' disappearance, is attacked in his home and later awakens to find a video from Jigsaw. The video reveals that Eric is still alive (having been saved and held captive by Jigsaw for six months after he was left for dead by Amanda), and that the only way to rescue him and Hoffman, who has also been kidnapped, is for Rigg to pass a series of trials that will teach him to let go of his obsession. If Rigg fails to pass his tests in 90 minutes, Eric and Hoffman will be killed.
Rigg finds a madam named Brenda bound to a chair in his living room and accidentally activates a trap, which partially tears her scalp off. He frees Brenda but she attacks him to evade arrest for her crimes, forcing Rigg to kill her in self-defense. Rigg is then instructed to abduct motel owner and serial rapist Ivan Landsness. He forces Ivan into a trap, which requires Ivan to blind both of his eyes to escape. Ivan only blinds one of his eyes, and the trap dismembers him. Next, Rigg is led to a school where he once investigated the abuse of a young student, committed by her father. He finds the student's parents are impaled with metal spikes: the father, Rex, has already died from blood loss, while his also abused wife Morgan remained alive at his expense by pulling the spikes from both of their bodies. Rigg gives her a key to free herself, then turns on a fire alarm and goes to the location of his final test.
Investigating Rigg's apartment, the agents find a clue that leads them to Jill Tuck, John's ex-wife, who reveals that she miscarried her son Gideon when Cecil Adams, a drug addict, slammed a door into her stomach while robbing her rehab clinic. The loss of their son enraged John and destroyed their marriage. At the motel, the agents learn that the room Ivan was killed in had been rented out to lawyer Art Blank, John's former business partner, and the survivor of the mausoleum trap. Art is revealed to be the man overseeing the current game when he hands Eric a gun. At the school, Strahm and Perez find a puppet, whose face explodes and sends shrapnel into Perez's face. While Perez is hospitalized, Strahm questions Jill and learns that John ended his work with Art after falling into depression, and that Cecil became the first victim of John's games. Strahm connects her story and a prior clue to discover the location of Rigg's final test: the Gideon Meatpacking Plant.
Strahm arrives after Rigg, but ends up following Jeff Denlon, who is trying to pass his own game. He finds Jeff in a sickroom with the corpses of John, Amanda, and his wife Lynn, and kills him in self-defense after Jeff points his gun at him. Meanwhile, Art pulls out a device that will free him, Eric, and Hoffman once the 90 minute timer expires; if used before then, a pair of pincers will sever his spine. Realizing Rigg's game is for him to wait until they are able to save themselves, Eric shoots Rigg as he is about to enter the room. Rigg opens the door nonetheless, triggering a mechanism that releases two ice blocks to crush Eric's head, and seemingly electrocutes Hoffman. After killing Art in self-defense, Rigg picks up the tape recorder he had on his person, which reveals that Eric would have lived if not for Rigg's obsession to save everyone. Hoffman then frees himself and leaves Rigg, who realizes that Hoffman was the actual third accomplice all along, to die from his gun wound. Before leaving, Hoffman also seals the door to the sickroom, trapping Strahm inside.
The film ends with Hoffman at the morgue, thus revealing that John's autopsy took place after the events of the film.