A young widower battles demons both actual and figurative in “Citadel,” a suburban nightmare with socioeconomic underpinnings.

After witnessing a brutal attack on his pregnant wife by a band of marauding kids, Tommy (Aneurin Barnard) is left with paralyzing agoraphobia and a baby daughter he can barely relate to. Goggle-eyed and clenched, trapped in an anonymous concrete desert where transport is scarce and utilities unreliable, Tommy finds solace in a warmhearted hospice nurse (Wunmi Mosaku) and therapy to modify his flinching body language. But when the fiendish imps — all wearing identical hoodies — return to claim his daughter, Tommy discovers there’s more to their viciousness than a lack of parental supervision.

Shot primarily in and around some crumbling tower blocks in Glasgow, Scotland, “Citadel” occasionally veers into ludicrousness, especially with the introduction of an angry priest (James Cosmo) who turns out to have a connection to the murderous minors. But this spare first feature from the Irish filmmaker Ciaran Foy (drawing on his own experiences) has an atavistic pulse, evoking a decaying society where elevators fail and bus drivers cower behind mesh grills.

Steeped in the fear of poverty, the film prompts us to wonder what’s gestating in those low-­income tower blocks: feral monsters or economically deprived delinquents? Its mind is already made up.