There are some heartwarming lessons to be learned in “Saw III,” the latest blood-soaked installment in the increasingly implausible horror franchise. First, that good help is hard to find. Second, that it is important to forgive your enemies and not become trapped in a quagmire of vengeance-seeking, for that way lies bitterness, anger, and possibly seeing someone’s head blow up.

The elusive killer called Jigsaw (Tobin Bell) is up to his old tricks again, putting people he deems worthy of scorn in elaborate traps from which they can only escape by torturing themselves. Except these latest schemes, the police notice with some degree of disappointment as they sift through the charred remains of Jigsaw’s latest failed pupil, lack a certain je ne sais quoi. They don’t bear the marks of Jigsaw’s usual discipline and to-the-letter fairness. What’s more, we know from “Saw II” that Jigsaw is dying of brain cancer, so he’s not apt to be up and about setting up torture chambers anyway.

Yep, ol’ Jig’s got himself an apprentice now, a former victim named Amanda (Shawnee Smith) who survived her test and is now learning to continue Jigsaw’s work. The current project: Teach a man named Jeff (Angus Macfadyen), consumed with hatred for his son’s killer, to move on with his life. The methodology: Put Jeff in situations where he can either watch the responsible parties die or forgive them and save them.

Meanwhile, Jigsaw himself is determined to survive long enough to see whether Jeff passes his tests or not. Weak and decrepit in a makeshift hospital room in his secret lair, he drafts an E.R. doctor named Lynn (Bahar Soomekh) to keep him alive at least until Jeff’s outcome is determined. The trick? If Jigsaw’s heart stops beating, a device rigged to Lynn’s body will kill her, too. Talk about the high cost of malpractice insurance!

The original “Saw” creators James Wan and Leigh Whannell are back as screenwriters (Wan was absent for part 2), and they’ve apparently caught “Lost” fever along with the rest of America. Every major character in the film gets flashback scenes, including a few that add a bit of texture to the events of parts 1 and 2. While not particularly relevant to the current proceedings, it is a nifty little present for the fans.

Also gift-wrapped and delivered free of charge to the fans? Lots and lots of pain, torture, blood and mayhem. Why, there’s even an instance of an electric saw being applied to the exposed skull of a living person — and it’s not even important to the plot! That one’s purely a freebie!

See all the Saws:

“Saw” (2004) B+
“Saw II” (2005) C
“Saw III” (2006) B-
“Saw IV” (2007) C-
“Saw V” (2008) D
“Saw VI” (2009) C
“Saw 3D” (2010) C-
“Jigsaw” (2017) B-

As an evil villain, Jigsaw stopped being scary as soon as they showed him to us. (I believe that’s actually Lesson 1 in Horror Films 101: Don’t put your “monster” in every single scene.) Now that he’s unequivocally the focus of the story, bedridden yet still remarkably lucid, continuing to ramble on about his elaborate “games,” he’s downright laughable. I remember the chills of his pre-recorded messages in the first film. Part 3 has nothing like that.

Part 3 also lacks a real protagonist. Jigsaw will die sooner or later, either from the brain cancer or from less natural means, so there’s no point worrying about him. Lynn doesn’t give us much to work with, and Jeff’s situation is so improbable — I don’t care how mad you are at the judge who let your son’s killer off the hook, you’re not going to just sit there and watch him die — that his “tests” lack any suspense whatsoever.

That leaves Amanda, whose attachment to Jigsaw is, you’ll pardon the pun, puzzling. I don’t understand her motivation for doing his bidding, much less why she seems to be in love with him. And a character you don’t understand is a character you don’t care about.

Like part 2, “Saw III” has been hyper-directed by Darren Lynn Bousman and over-edited by “Saw” regular Kevin Greutert. Even the non-torture scenes feel moody and depressed, all over-saturated in dark colors and scored with harsh, dour music. It’s a feel-bad film, for sure.

But is it an enjoyable feel-bad film? I guess. Is “enjoyable” even the right word? The whole stupid Jeff story aside, Wan and Whannell have a few clever ideas up their sleeves, and there is a bit more ingenuity in this chapter than there was in the last one. They’ve hacked out this audacious little niche for themselves, and I say more power to ’em. This is dark, superficially unsettling stuff (superficial in that the images won’t haunt you for any longer than the movie lasts), but if that’s what the kids want nowadays, “Saw III” more or less delivers it.

B- (1 hr., 47 min.; R, a lot of harsh profanity, some non-sexual nudity, abundant graphic violence, torture and gore.)