The Forever Purge, review: this satire on Trumpian mobs is neither subtle nor smart

• Dir: Everardo Valerio Gout. 15 cert, 103 mins

Horror franchises are rarely subtle, and the fifth instalment in the dystopian Purge saga lands with all the understatement of a cudgel across the back of the head. Shredded sinews, crushed skulls and oozing exit wounds abound in The Forever Purge. A visceral rip-roarer, it plays out like Max Mad crossed with The Walking Dead – but amid the spurting jugulars and the gunsmoke, director Everardo Valerio Gout chucks in barrel-loads of idealism.

Set in a near-future United States in which violent racists have taken their xenophobia to its logical conclusion by declaring an open-ended war of ethnic extermination, the film makes little secret of its real targets. It is clearly intended as a double-barrelled critique of real-world neo-Nazis. And if it goes about its business with a thudding lack of introspection, its noble intentions are clear.

The story opens with Mexican migrants Juan (Tenoch Huerta) and Adela (Ana de la Reguera) illegally crossing into Texas. Ten months later, Adela has found work in a factory. Juan, meanwhile, is employed as a farmhand on a megabucks ranch belonging to the decent but grouchy Caleb Tucker (Will Patten), his sullen son Dylan (Josh Lucas) and his tomboy daughter Harper (Leven Rambin).

They’re all about to batten down the hatches down for the annual “Purge” night, in which America’s citizenry is encouraged to let off steam in an orgy of violence and destruction. The twist in The Forever Purge is that the yearly bloodbath’s instigators, the Trumpian “New Founding Fathers of America”, have finally misjudged the forces they’ve unleashed.

Twelve hours of indiscriminate anarchy was never going to suffice for the extremists they’ve whipped up. These “patriots” have decided to defy the NFFA by declaring a “Forever Purge” – to last until America has been “purified of minorities”.

Previous Purge films, starting with 2013’s The Purge, had a streak of dark humour that elevated the material beyond mere horror fodder. However, The Forever Purge, written by series creator James DeMonaco, wears an earnest frown all the way through. As “Purgers” attack the wealthy Tuckers and give pursuit to Adela and Juan, the movie devolves into a sequences of bloody (but not particularly frightening) set-pieces.

Fleeing to the border city of El Paso with plans to cross into Mexico, Adela, Juan and the Tuckers (including Dylan’s pregnant wife, Cassie) are chased by feral hillbillies whose rotting masks make them look like rampaging zombies. A pitched battle in El Paso’s burning downtown district later recalls the Call of Duty video game. The dialogue could have come from a shoot-em up, too: “This country’s gone haywire. It don’t know itself no more” is typical of the clunkers the baddies are required to deliver.

But Gout marshals the mayhem with a whip-smart sense of momentum. Characters are thinly-sketched, the script rudimentary. And yet The Forever Purge careens ever forward, much like the Road Warrior-style Super-Nazis who eventually turn up in tricked-out off-roaders.

The Forever Purge lays on the political allegories with a blood-smeared trowel. However, it sprints from plot point to plot point in a lean and mean fashion. In so doing, it remembers the cardinal lesson of all decent horror movies: it’s perfectly acceptable for the story to be silly, even preachy, provided that it’s never dull.

In cinemas from Friday