The murder of a young man in a condemned tower block goes unsolved when police find not a single occupant willing to testify.
Three months later, the block comes under attack from a deadly sniper, picking off those close-mouthed residents one by one. Sheridan Smith, currently ubiquitous, leads the cast as a feisty singleton who organises the fightback.
The film offers a variant on the Colin Farrell thriller Phone Booth, inviting us to wonder who's the trigger-man – a random psychopath or a calculating avenger? There's just enough going on to keep us hooked.