Mum & Dad (2008) on Netflix

Mum and Dad, and their 'adopted' children, Birdie & Elbie, work at the airport. The family live off whatever they scavenge from cargo holds, offices and hotels - including a steady stream of transient workers who populate the airport's soulless hub. When Lena, a young Polish office cleaner, is befriended by Birdie, she gets drawn into a nightmarish world of torture, murder and perversity. Imprisoned in a suburban House of Horrors and designated a 'Mummy's Girl', Lena's only options appear to be to become part of the family - and join them in their insanity - or die.