It's a smaller, more compact and more standalone Saw film than the rest of the series. I'm a fan because of the way it constantly built out the mythology in ever widening circles of characters and backstories, but this one eschews all of that (apart from a mid credits sequence that sets a lot of that later narrative drive up).

And for what feels like the first time, it's actually about John Kramer (Tobin Bell) – he was never strictly a bad guy, but this time he's more overtly the hero; a kind, gentle, quiet man driven to become the Jigsaw killer in response to the mistreatment and unkindness of others.

It's not long after he's been diagnosed with the terminal brain cancer that kills him much earlier in the series (this film is set between the first and second instalments).

John sees a guy in his cancer support group looking hale and hearty at a coffee shop, they get talking and the guy tells him about a revolutionary but off the books treatment in Mexico from European scientists, far from the prying eyes of the FDA.

John sends them a message and their director, Cecilia (Synnøve Macody Lund) calls to tell John they want to help. He only has to get himself to a remote desert clinic in Mexico and they'll take care of everything.

He sends them a small fortune, flies to Mexico City and gets a taxi into the countryside before an unmarked van pulls up and blocks the road, masked men bursting out brandishing guns. But it's not a cartel kidnapping, it's the institute's goons, ensuring security by making sure nobody – not even patients like John – know where they are.

He's welcomed by Cecilia, the medical and care staff and a couple of other patients at the hostel where he'll be staying and told to relax in advance of his surgery a few days hence.

After the operation John wakes up and in a nearby hospital and Cecelia tells him the procedure was a complete success. Before he returns to the US he buys a gift for another patient he's befriended, Gabriela, but returns to the compound to find it trashed and abandoned, everyone gone and a video of brain surgery playing on a monitor near the bed he was supposedly operated on, revealing the whole thing to be a scam.

The game is on. His longtime accomplice Amanda (Shawnee Smith) helps him find and rounds up Cecelia, the fake doctors and nurses and fellow patient Gabriela, who he assumes was in on it (and who we learn in a flashback did it for Cecilia for drug money).

After they all wake up chained to walls in the clinic the scam took place, now a warehouse/factory full of scary, clanking machinery very much befitting a Saw film, John explains all their tasks and the order in which they'll complete them.

It starts as expected – there's a sawn-off leg, a decapitation, captives trying to reach a phone of a rolling trolley by using a small intestine as a rope, etc.

But another patient who was present while John was in Mexico, Parker, arrives outside – armed and angry, having been scammed the same as John was. John and Amanda talk him down and convince him to give up the gun and join in on their revenge, and he reluctantly agrees.

But at the first sign of bloodshed, Parker caves, having snuck back into the office upstairs to retrieve the gun, turning it on John and Amanda and demanding that Cecelia be let go.

In the only spoiler I'll give you in this review (because there are more, and they get bigger and better), Parker was in cahoots with Cecelia the whole time and she called him for help.

They pair force John and Carlos (the young son of the clinic's caretaker, who John bonded with and who's also shown up outside) into the device they assumed was made for them – a pivoting platform two people at either end can control, lowering their end by yanking a lever and being waterboarded... with blood.

As John does his best to save Carlos from the disgusting fate and starts to succumb himself, Cecelia and Parker leave them to drown in it and go upstairs to retrieve the bag containing John's payment still in the office safe. They pull the bag of cash out of the cabinet... and everything changes.

By this time (if you haven't already throughout the series) you're really rooting for John to come out on top and dish out the just desserts he's famous for, and he's never let you down – not just in the gruesome ingenuity of his traps but the way he's constantly one step ahead of everyone else there.

Whether he is or not I don't need to tell you (nor will I spoil the last few minutes), but suffice it to say it ends as satisfactorily as you hope.

Director Kevin Gruetert, who's been with the franchise as an editor and director since the first film, knows what he's doing from the script by incoming writers Josh Stolberg and Peter Goldfinger, and critics (of all people) were far more forgiving of this movie than most others in the series – maybe everyone was getting tired of the intricately twisted-up plot mechanics and characters.

It doesn't have quite the same worldbuilding ambition of the rest of the Saw franchise, but it has all the elements, Bell finally gets the limelight in his own movie, and the twist payoff will have you almost punching the air.