Ever wondered what Dementors do on their night off from Azkaban? Wonder no more as Spanish horrormonger Fresnadillo turns his attention from rampaging zombies to home-invading hoodies.
Actually, the title is a bit misleading as there's only one intruder – a cloaked spectre called Hollowface who steals into your home and tries to steal your face... if you're a boy.
Which makes him an obvious threat to a vulnerable lad like story-loving Spaniard Juan. So obvious that Juan's mum (the permanently worried-looking Pilar Lopez de Ayala) agrees to let Father Antonio (Inglourious Basterds' Bruhl) take a crack at his first exorcism.
If you're a girl, however, it's not clear what Hollowface is after. After coming to the attention of 11-year-old Mia (Purnell, the junior Keira Knightley in Never Let Me Go) in a scribbled story she finds stuffed in a tree trunk, he simply lurks around her bedroom until her construction worker dad John (Owen) becomes convinced they have a burglar.
To be fair, he does 'steal' Mia's voice, which leads to the intervention of psychologist Kerry Fox. But when a new security system provides no evidence of an intruder, Dr Fox, the police and Mia's mum (Carice van Houten) all assume that John has lost it too.
Similarly, Father Antonio's boss also pronounces Juan and his mother “nuts”.
Naturally, there's more to it than that. Or is there? It's hard to tell as Fresnadillo makes a pretty unconvincing job of bringing the two stories together.
Which is a shame, as the set-up is ripe with intrigue. Unfortunately, focus is frequently lost in the murky atmosphere.
A scare on a skyscraper proves to be no more than a laborious way of establishing John's unsettled state of mind, while a spot of nudity from van Houten turns out to be more gratuitous than any of her eye-opening scenes in Paul Verhoeven's Black Book.
Given the absence of bad language and gore, it's a curiously 15-certificate moment in a film that otherwise seems content to shock by 12-certificate suggestion.
Still, it does help to shake the feeling of deja vu as Fresnadillo makes several detours down Elm Street, splashes around in Dark Water, and sticks a tentative foot in Pan's Labyrinth.
Ultimately expecting too many allowances from its (ostensibly mature) audience, Intruders undoes a stealthy entry by tripping over its twist.