‘Heretic’ is a horror gem, and which works in the same way as when, in their prime, Robin Williams or Steve Martin, two comedy giants, would occasionally play against type as quite introverted, humourless characters (think Williams in ‘Insomnia’ or ‘One Hour Photo’ and Martin in ‘The Spanish Prisoner’) and would come across as chilling, psychologically dark actors who brought a real sense of menace to their performances. The same is almost true here with Hugh Grant who is at first the same romcom-friendly, flippant and even bashful and disarming figure we associate with his romcom heyday in the 1990s. He plays an English theologian, living in the US, who at first appears to relish the chance to entertain a couple of Mormon girls who turn up at his door to talk to him about the virtues of the Church of Jesus Christ of Latter-Day Saints.

But a friendly encounter with this eccentric figure starts to turn uncomfortable when the conversation moves from whether they want blueberry pie to what they think about polygamy. And the girls, who only entered his house because he convinced them that his wife was at hand, baking a pie in the next room, soon realize that they are trapped in his house, which resembles a church, and are unlikely to survive the night. Rather than let the girls teach him about Mormonism, Mr. Reed (Grant) exhibits a familiarity with the rudiments of theology and world religions, and produces board games and vinyl records to prove to the unsuspecting teenagers that all religions are iterations of another and that there is, as the adage goes, nothing new under the sun, rubbishing any claims that the girls may have that their faith is any more special than any other religions throughout history.

But, when pressured, Paxton (Chloe East) and Barnes (Sophie Thatcher) turn out to be far more intellectually able and resourceful than first appears, and a battle of the wills ensues. When they are asked to choose between two doors literally marked Belief and Disbelief, Paxton and Barnes show a deft awareness of how religious belief operates within a wider sphere of activity than simply presenting two binary positions. Grant plays a serial killer in much the same vein as Richard Attenborough in ’10 Rillington Place’, with Grant even doing an impersonation at one point of Attenborough’s slightly dodgy Scottish accent from ‘Jurassic Park’. We feel we know the Grant of this film – it’s the same Hugh Grant from so many other movies like ‘Four Weddings and a Funeral’ and ‘Notting Hill’, and when Paxton and Barnes realize that they are inhabiting a horror universe it corroborates the notion that people are rarely who they seem.

Grant does not go over the top or turn into a ranting, head-swivelling psychopath. He speaks rationally, politely, carefully and appears to be entirely sane… until the penny drops. The last act does come close to silly territory, as many horror films do, but this remains throughout a beguiling and intelligent horror which simultaneously engenders fear while giving us a lesson in comparative religion and mythology. Unusually for a horror movie, this is very wordy and the intellectual element persists throughout, and it feels as though this would work well on the stage. It’s not often that a horror film is quite this three-dimensional.