The film stars Sheridan Smith, Jack O'Connell, Ralph Brown, and Russell Tovey and entails residents of a block of flats targeted by an unseen sniper after witnessing the murder of a teenager.

The next morning Detective Constable Devlin (Steven Cree) conducts door-to-door enquiries about the previous night's murder, as the boy's body has been found.

Becky flees into the hallway, along with the other residents, as all the flats have been targeted: young couple Amy (Loui Batley) and Jeff (Michael Legge); Carol (Julie Graham) and her teenaged computer game addict son Daniel (Harry McEntire); chavvy single mother Jenny (Montserrat Lombard); middle-aged former soldier Neville (Ralph Brown) and his wife Violet (Jill Baker); small-time drug dealers Gary (Nabil Elouahabi) and Mark (Kane Robinson); lonely alcoholic Paul (Russell Tovey); and the violent petty criminal Kurtis (Jack O'Connell), who extorts protection money from his neighbours.

Becky, Kurtis, and Paul climb down the lift shaft, but discover the ground-floor exit door has been blocked with a skip and return to the top floor.

Jenny suggests the emoticons symbolise the three wise monkeys and that the sniper is targeting them because they let Jimmy be killed and refused to speak to the police about it.

Property developer Kevin (Christopher Fulford) and his assistant Eddie (Tony Jayawardena) arrive and spot the flames, but before they can call the fire brigade, the gunman shoots them both at close range.

Using this the three survivors manage to subdue the gunman and remove his mask, only to discover it is DC Devlin, who has cracked after endless lack of assistance in the cases he is investigating.

[2] Simon Crook of Empire rated the film 3 out of 5, stating, "An unusual, scuzzy setting for a thriller that delivers with brutal simplicity",[3] Sky Cinema also giving it 3 out of 5,[4] and Phelim O'Neill of The Guardian 2 out of 5, who wrote that: "It's not a bad idea for a movie, but what we get is undercooked, with poor logic and even poorer pacing conspiring to prevent any much-needed tension to build.

"[5] Jordan Mintzer of The Hollywood Reporter wrote from the Berlin International Film Festival: "Making up for its high concept/low brainpower scenario with some nifty action sequences and energetic performances, this rather promising directorial debut from duo James Nunn and Ronnie Thompson should foreclose at genre fests and ancillary outings worldwide.

"[6] Allan Hunter for the Daily Express "It doesn't sound like a great premise but this is surprisingly taut and involving thanks to some resourceful film-making and eye-catching acting.