Mike Flanagan’s Oculus is yet another movie, to add to a list that stretches into the afterlife, concerned with haunted families terrorised by demon squatters. Yet, despite reworking ideas well trod in Poltergeist and its recent spate of imitators and derivations, it has a few trump cards: a feisty and beautiful heroine in the form of ex-Doctor Who actress Karen Gillan, a story that skilfully interweaves the story of the principle characters’ macabre past with their equally unnerving present, and a dynamic between Gillan and brother Brenton Thwaites that’s suitably tragic, therefore affecting – at least more so than you’d expect in a story about a killer antique mirror.

Fans of Insidious, Sinister and the like, will just want to know what Oculus wants, and the answer appears to be, yes you’ve guessed it, souls. This 18^th century demon in a dress with a pair of silver eyes (it’s not clear how she got into the mirror or gained her ability to psychologically manipulate the living into committing murderous and self-harming acts but who cares) is the ultimate metaphor for a home wrecker. One imagines Flanagan’s family broke up following the discovery of an affair because the Lady in the Mirror does her upmost to destroy relationships and lay waste to families. “I’d have settled for IKEA” says doomed mother Katee Sackhoff when the foul bauble of man’s vanity is hung in the family home; as it’s as if Flanagan’s saying, “be happy with the modest things in life – your wife, your kids – it’s when you start craving something better that the trouble starts”.

In this “variations on a theme” movie, smart decisions count and Oculus can boast a few. In a film about eyes, Karen Gillan’s fine casting. Her peepers are large and inviting, capable of registering commitment, surprise and fear with equal intensity: in short, the perfect person to fight a spook with an ocular fixation. Having recently released mental patient Thwaites be the rationalist of the pair, with Gillan nevertheless trying to prove the existence of her childhood menace using the scientific method, is great fun for the audience – proving a proxy for their innate scepticism, some tech feitishism and a grounding for the shocks. It’s an old technique, as just about everything Flanagan throws at the audience is in this ghost story, but it works and the committed leads sell it.

Though derivative with an ending that’s telegraphed quite ahead of time, Oculus manages to grip thanks to Gillan’s personable contribution, the effective, sometimes surprising intercutting of timelines (a technique that gives the ending extra clout), and a sustained mood of eerie anticipation. At this point in the review it’s customary to note there can be few variants left in this horror sub-genre, but if we must have them, let them be tightly focused and well plotted like Flanagan’s nightmare.