During the gripping autopsy of the infamous Jigsaw Killer, John Kramer, a wax-coated microcassette is discovered within his stomach. Lieutenant Mark Hoffman is summoned to listen to the tape, which ominously indicates that he, too, is subject to a test, as the message reveals he is now “the last man standing.”
The narrative swiftly transitions to a foreboding mausoleum where two men, Trevor and Art, find themselves chained to a massive winch. In a twisted fate, Trevor has his eyelids sewn shut, while Art's mouth is similarly stitched, rendering any form of communication futile. The tension escalates as the winch begins to pull them closer together. Overwhelmed with panic, Trevor attacks Art, leading to a shocking turn of events where Art kills Trevor to obtain a key attached to Trevor's collar. In a further flashback, Art uncovers two crucial items in the mausoleum: a recorded message from Jigsaw himself and an envelope containing detailed instructions.
As tensions rise, the storyline reflects on the six-month disappearance of Detective Eric Matthews and the recent four-day vanishing of Detective Allison Kerry, as observed by Hoffman. The police make a grueling discovery when they locate Kerry's corpse, still suspended in the death trap that claimed her life in Saw III. After reprimanding Lieutenant Daniel Rigg for intruding through an unsecured door, Hoffman encounters FBI Agents Strahm and Perez. They deduce that Amanda Young, Jigsaw's accomplice, would not have managed Kerry’s trap alone, indicating additional collaboration in these heinous acts.
That same evening, a shocking attack happens at Rigg's residence, leaving him unconscious. Upon awakening, Rigg receives a distressing videotape informing him that Matthews is still alive and has just 90 minutes to escape, alongside Hoffman's life hanging in the balance. Thus begins Rigg's harrowing tests, where he discovers a woman named Brenda in a dire situation. Jigsaw urges Rigg to walk away and “see what I see,” but his instinct to assist cloud his judgment. When he removes Brenda's pig mask, he unwittingly activates a trap that slowly peels her scalp away. Although Rigg ultimately saves her, she believes Rigg has come to arrest her and assaults him in a panic.
After this tumultuous encounter, Rigg is led to a motel marked with the cryptic message "feel what I feel." Here, he must abduct the manager, Ivan, a serial rapist. Furious at discovering the evidence of Ivan’s crimes, Rigg forces him into a preordained trap, offering him a nightmarish choice between blinding himself or facing gruesome dismemberment. Under pressure, Ivan makes a desperate attempt to avoid total annihilation but ultimately succumbs to the cruel fate that awaits him.
Rigg’s next test brings him to a school where he comes face to face with Rex, the abusive husband of Morgan and father of their daughter Jane. The scene reveals a horrifying tableau: Rex and Morgan are impaled together, their lives precariously intertwined. For Morgan to save herself, she must have the courage to pull out the rods impaling Rex, essentially sealing his fate. Rigg arrives at a critical moment to encourage Morgan, as she fights through shock and blood loss to save herself, ultimately alerting emergency services before leaving the site.
As the investigation unfolds, Strahm and Perez become painfully aware that they, too, are targets within this deadly game, leading them to discover that all victims were defended by Art, who also has ties to Jill Tuck, John Kramer's ex-wife. In a grim twist of fate, the story connects back to Jill's traumatic past when she lost her baby Gideon, igniting John's series of vengeful traps against those who harmed them.
As the tension mounts, it becomes evident that the final act of Rigg’s path leads him to Art, Matthews, and Hoffman, who find themselves undergoing their own trials amid the relentless countdown. With each passing moment, lives hang in the balance, and the gut-wrenching conclusion unveils the ultimate lesson borne from sacrifice and failure. Rigg's desperate measures result in devastating outcomes, culminating in a shocking revelation about Hoffman and the dark web of Jigsaw's manipulations, as reality blurs with the memory of past horrors.
In the end, as the film weaves a complex narrative filled with heart-stopping moments, Jigsaw's postmortem reveals the cruel irony that these events were far from over, forever linking the lives of those ensnared in his sinister plans.
