Months after a youth is murdered on the top floor, the last remaining residents of a condemned high-rise find themselves under fire from a ruthless sniper. Whether loners, lowlifes or people with loved ones, the terrified neighbours must put aside their differences if they're to have any hope of getting out alive. Sheridan Smith tries to keep her head in a British suspense thriller that takes no prisoners.
West End stage star Sheridan Smith is Becky, one of the top-floor occupants of the ironically named housing block Serenity House who, for reasons unclear, steadfastly refuse to move when everyone else has left.
You'd have thought the less obnoxious ones (Becky, the stoical older couple, the parents with the nerdy teenager, the lonely alcoholic) would jump at the chance to be rehoused somewhere potentially less grim.
But no, instead they choose to live alongside a shriekingly abusive single mother, a constantly bickering couple and a pair of doped-up wasters. All this while paying protection money to the biggest scumbag of the lot: Kurtis the drug-dealing Northerner (a brilliantly repulsive Jack O'Connell).
Anyway, one Saturday morning Becky is just getting to know the bloke she just woke up with when... well, let's just say if it wasn't his first one-night stand, it was definitely his last.
In one chaotic minute, it becomes clear that the block is under attack from a shooter who, given clearance by the IOC, would easily pass Michael Phelps' gold medal tally in a single Olympics.
Able to hit anything that moves in any of eight distant flats in a split second, the gunman soon has the survivors of his opening salvo cowering in the communal corridor.
What's more, once everyone stops arguing (the phrase "pull your head in" never seemed more appropriate) and starts to think about how they might escape, they find their assailant has not only cut all communications but left more nasty surprises on the inside.