A case could be made that “The Texas Chainsaw Massacre” remake (2003) wasn’t worth doing – although I found it fun as an alternate narrative. But if its purpose was to pave the way for “The Texas Chainsaw Massacre: The Beginning” (2006), it was worth it. This 1960s-set prequel shows no signs of playing things cautiously, the bane of many backstories.

A fantastic Final Girl

Also to its credit is Jordana Brewster, who shows massive improvement since breaking out in “The Faculty” (1998). As Chrissie, she’s the saga’s best Final Girl since Marilyn Burns, deliciously bridging the gap between victim and fighter.

This entry from director Jonathan Liebesman (2014’s “Teenage Mutant Ninja Turtles”) is horrific. But it’s also an intense action thriller — even if it eschews a complex plot and gets right to the adrenaline of hunts and chases. It’s enhanced by Steve Jablonsky’s dread-dripping score.

“The Texas Chainsaw Massacre: The Beginning” (2006)

Director: Jonathan Liebesman

Writers: Sheldon Turner (screenplay, story), David J. Schow (story)

Stars: Jordana Brewster, Taylor Handley, Matt Bomer

Chrissie gets split up from her three friends – boyfriend Eric (Matt Bomer), Bailey (Diora Baird) and Dean (“Hidden Palms’ ” Taylor Handley) – in a car crash, then tracks them down at the Hewitt house.

Brewster expresses the right amount of shock at everything Chrissie discovers. It becomes new for us, even though we already know how the Hewitts operate: using unwary travelers for meat since the closing of the slaughterhouse.

“The Beginning” consciously addresses accusations of selfishness in survival situations in horror films. More than once – including when the film indulges in a claustrophobia-breaking long shot of the Hewitt house – one of them could run away. But they know that would doom their friends.

Ermey steals show from Leatherface

A scene stealer on the villain side is again R. Lee Ermey as the Hewitt patriarch who takes up the guise of Sheriff Hoyt. He dispatches the outgoing dying-town sheriff with “Damn, I just killed the entire police department!,” one of several pitch-black one-liners.

And darker than dark: the way the stump-legged Uncle Monty (Terrence Evans) from the ’03 film loses those limbs. It’s so twisted that I wonder if the ’03 movie made him legless just to set this up.

It’s an open secret by now that Leatherface (Andrew Bryniarski) isn’t the focal point of his own movies. He’s a weapon dispatched by Hoyt.

Writer Sheldon Turner (“X-Men: First Class”) opens with the deformed baby’s birth in the 1930s – in the slaughterhouse, natch – then makes the closing of the plant into a grim commentary on the emotional toll of layoffs. Leatherface isn’t just losing a job, he’s losing his lifestyle.

But I didn’t embrace Leatherface as a misunderstood human being as much as in some other entries. Maybe it’s because his killings and face-cuttings are so gruesome that “The Beginning” makes an even stronger case than its predecessor for the “torture porn” label.

War trivial by comparison

It’s also because Turner explores a lot of issues outside of Leatherface’s plight – most tellingly, the Vietnam War, as Eric and Dean have different ideas about whether they’ll report for the Army. It’s too generous to say the horrors they then experience in Texas are a commentary on ’Nam.

But it’s common for horror films to start off exploring an issue and then lose sight of it. Indeed, it’s built into the genre. And it’s purposeful here: “The Beginning” illustrates the devolution of humanity as the crisp plots, arcs and themes blur into a pure survival story.

The “patriotic” concept of killing people on the other side of the globe you have no beef with turns into a trivial issue. The Hewitts are ahead of the curve: already animalistic.

A Vietnam debate seems quaint by the time Leatherface is swinging his chainsaw in pursuit of Chrissie, now caked in her friends’ blood.

“The Beginning” marks the end of a two-film detour into an alternate narrative, but what a way to go out. Between the link-ups, Brewster’s emotive Final Girl and the ceaseless dread and horrific happenings, this is the best “Chainsaw” since the 1974 original.

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My rating: