Where would horror movies be without the good ol’ American concept of the “abandoned warehouse”? This fictional setting is crucial to the logos, albeit meager, of “Saw III,” which promises gross-out violence, filleted corpses and that horror of horrors, dim overhead lighting.

Jigsaw, already unmasked as death-ridden cancer patient John Cramer (Tobin Bell), returns ready to set up his victims — and his audience — to torture and punish themselves. Thankfully, he’s got a knack for creative discipline and room enough in the aforementioned warehouse for eye-popping contraptions so over-the-top they make the Spanish Inquisition look like a tickling contest.

Yes, the days are long gone when it was enough to watch D-listers remove their own appendages with a Black & Decker. Now, in “Saw III,” they dip their extremities in skin-eating acid, rip off chains pierced like jewelry to their sides and struggle to save themselves from drowning in a vat of rotted pig guts. (Note to movie-marketing people: Reconsider running the trailer for the new “Charlotte’s Web” before “Saw III,” in which we see a series of blue-veined, naked hog carcasses pureed into Wilbur Soup.)

The first 20 minutes or so of “Saw III” try to make it look like something it doesn’t turn out to be — a continuation of the series’s first two installments. The way things start out, it looks like we’ll be following Detective Kerry (Dina Meyer from “Saw” and “Saw II”) as she struggles to stop a spree of gruesome murders that are eerily reminiscent of the supposedly deceased Jigsaw killer. But then suddenly, out of nowhere, Kerry is kidnapped, tortured and savagely ripped apart by a, um, rib-removing device.

Cut to Iranian-American actress Bahar Soomekh (“Crash”), whose critical acclaim landed her the role of dour doctor Lynn Denlon. Before viewers have had time to search their database of past “Saw” characters, inductee Denlon is kidnapped, strapped with explosives and forced to use her mad medical skills to keep Jigsaw alive. If he flat-lines, then the (oddly flattering) mechanical collar she wears around her neck will detonate, turning her head into a pulpy stain on the wall.

Meanwhile, Jigsaw’s masochistic, former-drug-addict assistant Amanda (played by Shawnee Smith, also from the first two films) sets in motion a bloody obstacle course for troubled father Jeff (Angus Macfadyen.) He must play a series of games in which the lives of people he hates are at stake. Forced into moral dilemmas — like whether to take a bullet to the face or watch the man responsible for his child’s death get slowly twisted around — he makes some interesting choices, none of which make a whole lot of sense.

Additionally, there are some stunts in “Saw III” that seem as painful to watch as they would be to actually endure. For example, ever wonder what it looks (or feels) like to have someone remove part of your scalp, drill a hole in your skull and then remove part of your brain — all while you’re fully conscious? It probably feels kind of like watching it happen to someone else. Watching a movie like this is the intellectual equivalent of literally removing parts of your brain. It’s trash that knows it’s trash. Like late lamented couple Kevin Federline and Britney Spears.

“Saw III” is not better or worse than either of the first two films. How can it be when it is the same film? No, seriously. Huge chunks of “Saw III” are merely flashback footage from the previous two films, apparently thrown in to remind us what happened. And get this: Word has it that the makers of “Saw III” were so cheap that they borrowed the set used by the makers of “Scary Movie 4” to make fun of “Saw” and “Saw II.”

The second-most annoying thing about “Saw III” is that it tries to make some kind of moral statement about appreciating life and learning to forgive. What’s absolutely most frustrating is that it feels the need to justify every tangential, time-buying plot point with a long, completely ridiculous explanation. Hearing Tobin Bell’s hoarse, fake cancer voice rattle on incessantly about how one story line relates to the other only provokes a desire to have his cancer quickly eat out his vocal cords, rendering him mute.

A disappointingly dull blade raking on our nerves, “Saw III” reminds us that it doesn’t take long for cheap horror dynasties to rust and rot. Despite some box-office success, it looks like it’s time for Jigsaw to hand in that creepy clown mask, return to his abandoned warehouse, polish his collection of tape recorders and die. Again.