The film kicks off with Seth, portrayed by Joris Jarsky, trapped in a deadly pendulum mechanism. It soon emerges that Seth is a murderer, having been released from prison early due to a legal technicality. A puppet, symbolic of Jigsaw, presents Seth with an ultimatum: to rescue himself, he must destroy the tools of his murderous trade—his own hands. Although the trap appears to offer a chance of survival, it is ultimately revealed to be unwinnable. Seth believes he must press buttons in two separate devices, which will crush his hands simultaneously before the descending pendulum, meant to bisect him, finalizes its grim task. Despite grasping the futile nature of his struggle, he goes ahead and crushes his hands, but the pendulum continues its deadly descent, leading to a gruesome end witnessed by an unseen watcher through a peephole.
Simultaneously, Agent Strahm, played by Scott Patterson, is seen in a chaotic pursuit of the truth. He shoots Jeff, a character brought to life by Angus Macfadyen, before entering the scene of Jigsaw's death. As he investigates, Strahm discovers Jigsaw's lifeless body, only to find himself trapped when fellow agent Mark Hoffman, played by Costas Mandylor, locks the door behind him. In a twist of fate, Strahm stumbles upon a concealed door marked with glow-in-the-dark paint. When he hears Jigsaw's voice on a recording, it warns him against continuing his quest for truth, suggesting that his "insatiable hunger" may lead him further into darkness. Ignoring the warning, Strahm ventures down a mysterious corridor, only to be ambushed by an assailant in a pig mask—presumably Hoffman. The agent subsequently finds himself ensnared in one of Jigsaw's traps, his head enclosed in a sealed container that fills with water. In a desperate bid for air, he resorts to performing a tracheotomy using a nearby ballpoint pen.
As events unfold, law enforcement arrives at the Gideon Warehouse, where Hoffman is later seen carrying Corbett, a character portrayed by Niamh Wilson, whom he claims to have saved. Despite sustaining critical injuries, Strahm is loaded onto a stretcher, clinging to life. The following day, a memorial service is held for those who succumbed in the pursuit of Jigsaw. During this solemn occasion, the Chief of Police announces the end of the Jigsaw murders and lauds Hoffman with a promotion. Meanwhile, Jill, John Kramer’s ex-wife played by Betsy Russell, receives an important videotape and box from John’s attorney. The contents of the box remain undisclosed, and Jill departs without divulging the details.
Strahm mourns the loss of his partner, Agent Perez, voiced by Athena Karkanis, who has died overnight. His superior, Agent Erickson (Mark Rolston), informs Strahm of his reassignment off the ongoing Jigsaw case, leaving Strahm frustrated and angry. Hoffman's demeanor appears suspiciously calm during this turbulence. In his own office, Hoffman discovers a note reading "I know who you are," heightening his sense of peril as he fears his hidden identity as Jigsaw’s disciple may be exposed.
Meanwhile, five individuals regain consciousness in a sewer, caught in a sinister necktie trap. The puppet prompts them to cooperate or face deadly consequences, as they must retrieve keys to escape the impending doom of beheading. The urgency intensifies as explosive devices are triggered on a countdown. Characters like Mallick (Greg Bryk) exhibit panic, resulting in rash decisions that lead to one of the group, Ashley (Laura Gordon), ultimately falling victim to the test by the guillotine's blade.
Strahm, trying to piece together the threads of his investigation, scours FBI databases for any leads on Hoffman and uncovers the tragic link between Hoffman's sister’s murder and Seth's demise. It becomes evident that Hoffman has manipulated the narrative to absolve himself of blame in Seth's death, which Serves as a dark realization for Strahm. This unveiling is marked by flashbacks where Hoffman carefully orchestrates his plans while Jigsaw compels him into servitude.
The trials for the five in the sewer turn more deadly. In their next challenge, they must shatter jars to obtain the keys necessary for survival as bomb detonations loom. Ruthlessness surfaces as characters betray one another in a desperate scramble for survival, leading to chaos and bloodshed. Tension peaks as they arrive at a final challenge requiring them to bleed into a shared beaker to unlock their path to freedom. The tragic irony unfolds when they realize that, had they worked together, they could have saved each other and lived.
As the horrifying spectacle develops, Strahm engages in a perilous chase after Hoffman, ultimately leading him to a new location—a house from a prior movie where past horrors linger. There, he encounters a trap set by Hoffman designed to catch him off guard. With time running out, Strahm’s fate hangs precariously in the balance as Hoffman lures him deeper into a game where trust is the only chance for survival.
With a swift turn of events, Strahm finds himself entangled in the very trap he was investigating. This ultimate twist leaves Hoffman a free man, poised to continue Jigsaw's legacy undetected and unchecked. As the film culminates, Hoffman emerges as the final survivor in this grim cycle, with Strahm’s demise marking a definitive end to their cat-and-mouse game, locking in a fate that echoes the haunting legacy of Jigsaw himself. In the lingering aftermath, the shadows of past deeds loom large, suggesting the terrifying legacy of 'Saw' is far from over.
