History Film / SawIV

** Brenda's trap wouldn't scalp her in real life. The hair would rip and tear before the scalp would. Hair might be strong, but it's not that strong.

* PetTheDog: Rigg gives Morgan his coat after finding out what happened to her, and although he doesn't stay when she begs him to, he yanks the fire alarm on his way out, ensuring she'll be saved.

* PoliceAreUseless: Somewht played straight. Rigg is essentially "recruited" to stand in for Jigsaw for his tests. Eric is psychologically broken, to the point he tries to kill himself in his new trap, and [[spoiler: The only other key cop from the local precinct we've met, Hoffman, is also in a trap, and ends up being Jigsaw's other apprentice.]]

* RiddleForTheAges: Unlike all the other victims, Trevor's reason for being targeted by Jigsaw was never explained.

** Despite knowing they're dealing with a SerialKiller specializing in homemade traps, Perez [[spoiler:leans her face toward a suspicious-looking Billy and gets a face full of shrapnel for it]].

* JustInTime: An unique subversion. [[spoiler:Rigg reaches the room where Eric's trapped right when the timer is at one, only to find out that he was supposed to get there in ''over'' 90 minutes, and since he got there before the timer reached zero, Eric gets killed.]]

* JerkWithAHeartOfGold: Agent Strahm. He's brusque and doesn't suffer fools easily, but he treats his partner, Perez, with complete respect, [[spoiler: Even breaking down in tears after calling her family and informing them she was critically injured by a Jigsaw trap.]]

* FBIAgent: The film introduces us to Special Agent Peter Strahm, and Agent Lindsey Perez with the FBI. Even though they get overwhelmed eventually, they're presented as much more capable in the situation than the local police department ever was, and reveal they were also assisting Det. Allison Kerry in her Jigsaw investigation behind the scenes.

* JurisdictionFriction: Upon the arrival of Agents Strahm and Perez, they basically inform Det. Hoffman that they're taking over the Jigsaw investigation, and local law enforcement will be support only.

* DeathOfAChild: [[spoiler:Jigsaw and Jill lost their son Gideon to a miscarriage Jill suffered while her health clinic was being robbed.]]

** Being Jigsaw's first designed trap, the Knife Chair was fundamentally flawed, and [[spoiler:Cecil]] quickly freed himself from it because the chair gave away before he could fully pass his face through the blades.

** Being Jigsaw's first designed trap, the Knife Chair was fundamentally flawed, and [[spoiler:Cecil]] managed to free himself from it because the chair gave away before he could fully pass his face through the blades.

** Being Jigsaw's first designed trap, the Knife Chair was fundamentally flawed, and [[sspoiler:Cecil]] managed to free himself from it because the chair gave away before he could fully pass his face through the blades.

* SurprisinglyRealisticOutcome: [[spoiler:Cecil doesn't develop StockholmSyndrome or forgive John for putting him in a death trap. No, he's royally pissed off and once he gets out, he immediately bum-rushes John with every intent of kicking his ass.]]

* SurprisinglyRealisticOutcome: [[spoiler:Cecil doesn't develop StockholmSyndrome or forgive John for putting him in a death trap. No, he's royally pissed off and once he gets out, he immediately bum-rushes him with every intent of kicking his ass.]]

* WaitingPuzzle: A variant. Rigg is instructed by a tape that he has a timer of 90 minutes to get to the room where Eric could potentially die in. [[spoiler:When he gets to the entrance and goes through it despite Eric's plea for him not to do so, Rigg finds out that the timer referred to the time he had to wait in order to enter without worrying about Eric getting killed.]]

* DarkerAndEdgier: This film is even gorier than ''Saw III'' (which was already dark when compared to the first two films), and features some very heinous victims, including a pimp, a serial rapist and a domestic abuser. As if the DeathOfAChild from ''Saw III'' wasn't enough, this film explicitly depicts [[spoiler:the [[ImperiledInPregnancy miscarriage of an unborn baby]]]] in a flashback.

* DarkerAndEdgier: This film is even gorier than ''Saw III'' (which was already dark when compared to the first two films), and features some very heinous victims, including a pimp, a serial rapist and a domestic abuser. As if the Death of a Child from ''Saw III'' wasn't enough, this film explicitly depicts [[spoiler:the [[ImperiledInPregnancy miscarriage of an unborn baby]]]] in a flashback.

* DecoyProtagonist: The last minute or so of the previous movie sets Jeff up as the protagonist for this one - "In order to save your daughter, you will need to play a game." Apparently, the new writers brought in for this movie didn't want to follow up on that plotline, since Rigg is instead the main focus and [[spoiler:Jeff is later shot by Strahm]].

* TragicKeepsake: Bobby the Puppet, the doll from which Billy the Puppet was inspired, is this for John. It's all but stated that John has kept Bobby around as a reminder of his lost child.

* SentimentalHomemadeToy: Bobby the Puppet is a harlequin doll that John had made for his unborn son Gideon, and he became very possessive of it during his depression after [[ImperiledInPregnancy Jill's miscarriage]]. In one flashback, John is seen softly touching Bobby after putting it back on a table from which Art accidentally knocked the doll over. Bobby itself would eventually become the basis of the design of the [[Franchise/{{Saw}} franchise]]'s iconic Billy the Puppet, and was later seen in the background of ''Film/SawV'' and ''Film/Saw3D''.

** The room at the motel where the Bedroom Trap is set bears a resemblance to Adam's backroom in the first film with its red lightning and scattered photos.

* TheSmartGuy: Strahm is set up as being smarter and more competent in the investigations than all the law enforcement officers prior. As the first who rules out that Amanda wasn't solely responsible for putting Kerry in the Angel Trap and that John couldn't have assisted her due to his condition at the time, he makes it clear within the first moments of his introduction that he deduces Jigsaw must have a second apprentice beyond Amanda. Later, he figures out that the Urban Renewal Group's motto "four walls build a home" could reference the Gideon Meatpacking Plant. Unfortunately for him, things with the other cops (including fellow agent Perez) get out of hand so thoroughly that even with his intelligence, the situation overwhelms him a good deal.

* TheSmartGuy: Strahm is set up as being smarter and more competent in the investigations than all the law enforcement officers prior. When they find Kerry's corpse, he immediately rules out Amanda as solely being responsible for putting Kerry in the trap, stating that Amanda, who was pounds lighter than Kerry, wouldn't have been able to lift her into it, and stating the "bedridden cancer patient" John Kramer also couldn't have assisted her. As the first who rules out that Amanda wasn't solely responsible for putting Kerry in the trap and that John couldn't have assisted her due to his condition at the time, he makes it clear within the first moments of his introduction that he deduces Jigsaw must have a second apprentice beyond Amanda. Later, he figures out that the Urban Renewal Group's motto "four walls build a home" could reference the Gideon Meatpacking Plant. Unfortunately for him, things with the other cops (including fellow agent Perez) get out of hand so thoroughly that even with his intelligence, the situation overwhelms him a good deal.

* TheSmartGuy: Special Agent Peter Strahm's introduction sets him up as smarter than all of the cop protagonists in the films prior. When they find Kerry's corpse, he immediately rules out Amanda as solely being responsible for putting Kerry in the trap, stating that Amanda, who was pounds lighter than Kerry, wouldn't have been able to lift her into it, and stating the "bedridden cancer patient" John Kramer also couldn't have assisted her. He then makes it clear that within the first few moments of his introduction, that he knows that Jigsaw had a second apprentice beyond Amanda. [[spoiler: He also seems to have a good bit of disdain to Det. Hoffman, seemingly on instinct. An instinct that proves to be right when it's revealed that Hoffman is the second Jigsaw apprentice Strahm has been looking for.]] Later, he's also the one [[spoiler: that figures out "four walls build a home," is referencing the Gideon Meat Packing Plant.]] Unfortunately for him, things get out of hand so thoroughly that even with his intelligence, the situation overwhelms him a good deal. [[spoiler: Perez being critically wounded by one of Jigsaw's traps doesn't help his psyche either, especially when we see him making the call to Perez' family that she's in the hospital, condition unknown.]]

* WhamShot: [[spoiler:Rigg's recklessness ends up killing everyone in his final test, supposedly including Hoffman, who was strapped to an electrified chair that would electrocute him with the water from the melting ice block that Eric was on top off before his death. Immediately after Rigg plays Art's tape, Hoffman is seen standing up and walking from the background behind Rigg, without any signs of having been actually electrocuted.]]

And indeed, a young cop named Daniel Rigg obsessed with rescuing Jigsaw's victims finds himself thrust into one of his games, with the lives of Eric Matthews and Hoffman on the line as he makes his way though the city to find clues to their location, finding other unfortunates along the way who are likewise in the midst of Jigsaw's deadly game.