It would probably be overstating it to suggest that Ciaran Foy has any sort of cult following. But, since the release of his spooky short The Faeries of Blackheath Woods in 2006, the movieverse cognoscenti have been counting the days until the Dubliner's first feature release.

Citadel doesn't disappoint. Drawing from his own experiences of agoraphobia following a brutal mugging, Foy has taken the emerging genre of "hoodie horror" (Eden Lake, Them) and pushed it in novel and disturbing directions. You'll jump. You'll cower. You might think just a bit.

Set in a grim version of urban Scotland (but really AnyDump, Anywhere), Citadel begins with Tommy (Aneurin Barnard), trapped in a lift, watching helplessly as his pregnant wife is savagely attacked. After giving birth, she dies and Tommy is sent into the world with his new daughter and a weighty basket of neuroses.

Little whispers of Roman Polanski's Repulsion sound as the protagonist cowers in his flat while hoodlums circle outside. Just because you're paranoid doesn't mean quasi-supernatural trolls aren't planning to eat your brains. An impressively deranged priest (off-the-leash James Cosmo) explains that we may be dealing with actual, rather than metaphorical, demons: blind, feral, unthinking. A fight-back is launched.

The final catastrophic clashes between Tommy and the malign entities are handled nicely but, as is often the case with such things, the film is at its best during the slow, steady accumulation of urban unease. Tim Fleming shoots in a sickening blue-grey light that suggests the very air is thickened with disease. Coming across like an even nervier Sam Reilly, Barnard is entirely convincing as a man knocked sideways by the manifestations of his own psychoses.

Some may argue (indeed some already have argued) that Citadel demonises the urban underclass. But this is no Yuppie nightmare. Tommy really is an emanation of the urban working-class. By way of contrast, the monstrous villains – standing in for fears we all share – are not really of this earth. Serious thinking has taken place.

We expect great things from you, Mr Foy. Nothing less.