Fortitude finale - ramps up the crazy and goes out on an explosive high

“Is Dan Anderssen a good sheriff or a bad sheriff?” wondered one character when Fortitude (Sky Atlantic, Thursday, 9pm) first began. The question was rhetorical – there was no crime in Fortitude, the northernmost settlement in the world and “the safest place on earth”. While fatal attacks were not unheard of, the polar bears that committed them generally avoided arrest.

Gruff, grizzly and clearly territorial himself, maybe Richard Dormer’s sheriff harboured a beastly prejudice. Dormer’s terrific performance has become more growling and sinister (and darkly comic) as Sky’s second series has progressed, frequently gnashing at the genre boundaries of the show to see how much it can contain.

If Dormer’s Anderssen became the show’s natural focus at the expense of all else, it’s partly because he straddles the divide between a police procedural and a horror show most effortlessly: even in the grip of demonic possession, the good sheriff/bad sheriff question is hard to settle.

In truth, though, eventually he had little competition as the rest of the cast was gored, butchered, beheaded, incinerated, fatally infected, crushed, drowned, defenestrated or – less frequently – shot. He was simply the last person prowling.

That ramping up of crazy means the show is best watched in a quibble-free binge, and yet writer Simon Donald’s narrative has been allowed to drift.

A long-anticipated showdown between Anderssen and Robert Sheehan’s boyish shaman, Vladek, pitched as a battle between good and evil, was roundly decided in evil’s favour. In the finale, an abrupt manhunt for Anderssen, now believed to have healing powers that science can exploit, serves only as a perfunctory excuse to off any remaining baddies and blow the rest of the pyrotechnics budget.

Is it any wonder that only Dormer, resplendent in bulky furs and finally given to eating his prey, seems truly at home? Fortitude’s blend of the forensic, scientific and supernatural deliberately seeks out a terrain of thinnest ice. Modelling his performance on the ferocity and even weighting of a polar bear, Dormer alone knows how to walk on it.