A military cargo plane has crashed, leaving its highly classified contents strewn across London. Unaware that the city is on lockdown, Charlie (Noel Clarke) and Shelley (Antonia Campbell-Hughes), accompanied by best friends Mark (Colin O'Donoghue) and Nikki (Laura Haddock), are at a storage facility of the film's title name, dividing up their possessions. Suddenly, the power goes off. Trapped in a dark maze of endless corridors, a mystery predator is hunting them one by one. In a place designed to keep things in, how do you get out?