"I guarantee everything will seem fine in the light of day..."
Oh dear. Those cheery words come back to haunt cocky squatter Toby (Maguire) as he faces his first night in what appears an ideal gaffe to enjoy a life unencumbered by rent.
He's persuaded his art school chums, the nervous Molly (Malin), feisty punkette Zoe (Noble) and posh kid Luke (Biggs) to share his new, not-quite-legal, home.
It's a rambling, derelect pile in an anonymous London terrace which Toby secures with his own lock and then distributes a set of keys to his fellow squatters.
The trouble is that during the night someone replaces Toby's lock with their own, considerably bigger one. It's only then that the foursome discover that the windows are blocked with sheet steel and every entrance has been bricked up.
Further exploration of the labyrinthine residence reveals a warren of bleak rooms and the very real possibility that there's someone - or something - in there with them.
Writer-director Daniel Simpson ratchets up the tension, fully acquainting viewers with the soon-to-be victims before letting fly with an all-daggers-stabbing orgy of violence as the terrified foursome are cut down to size.
It's not for the squeamish - one scene features a particularly unpleasant eyeball pluck - but most of the mayhem is suggested rather than falling into the torture-porn trap of full sadistic disclosure.
Perhaps the housing association option isn't such a bad one after all...