Tommy Cowley (Aneurin Barnard, Ironclad) lives a quiet life in a decaying apartment complex with his very pregnant wife. The couple is attacked one day by a group of hooded young thugs, and after a shocking act of violence, Tommy is left to raise his newborn daughter alone - forever traumatised by the attack.
Suffering from extreme agoraphobia, Tommy alternates his days hiding out from imagined threats in his new apartment and intense therapy sessions aimed at bringing him back to normalcy. But when the same hooded gang return to terrorise Tommy again, he's torn between his paralyzing fear and protective parental instinct.
With the help of a vigilante priest (James Cosmo, Braveheart) who has uncovered the genesis of this ruthless, potentially supernatural gang, Tommy must overcome his fears and venture into the heart of the abandoned tower block known as the 'Citadel' to save his family.