10 Awesome Horror Movie Twists You Never Saw Coming
5. One Twin Was Dead All Along - Goodnight Mommy
An Austrian movie about two twin boys who suspect something is wrong with their mother, Goodnight Mommy slowly ramps up the tension as it devolves into the weirder and weirder - with Elias and Lukas stopping at nothing to figure out the truth of who they believe to be an imposter. When their mother returns from cosmetic surgery with bandages on her face and a whole new attitude towards her children, the pair end up trapping her in their home until she is honest with them - though we eventually learn at the end that she hasn't once told a lie.
Despite seeding clues throughout that the mother has been replaced by a lookalike, it's actually the twins that aren't what they seem, with the twist culminating in the reveal that Lukas died in an accident before their mother came back home. Her inability to see Elias's hallucination of his brother results in him tragically burning the house down - making the whole thing even more of a harrowing experience when we finally get to the end. Never trust twins in a horror movie, eh?