Horror works best when it takes you by surprise. The fear of the unknown is what drives the scariest of stories, after all, whether it's monsters wilder than your darkest imagination or the black void staring back at you when all the lights have gone out - so dumping a big fat plot twist into your movie is the best way to replicate that and scare your audiences sh*tless. A good twist really is something that breaks a film or commits it to eternal adoration, as anyone that's watched High Tension can vouch for in either direction.
Narrative left turns that come out of nowhere and actually stick the landing really are horror movie gold dust, and transforms the arbitrary into the awesome. What's scarier - your average, boring, zombie redneck torture family, or a zombie redneck torture family controlled by a government operation designed to stop us being totally annihilated by a race of ancient gods?
Your honour, I rest my case.
10. Esther Is A 33 Year Old Psychopath - Orphan
When you adopt a sweet girl into your young family, you'd expect there to be a settling in period. But for 9 year old Esther, as she's welcomed into the Coleman's lives, she seems almost too good to be true. A talented artist, a kindly sibling to Max and Daniel, and remarkably mature for her age, Esther fits in like a dream to Kate and Jon's situation, coming as a breath of fresh air after tragically losing their third child in a still birth.
She's their golden child. Or at least, she is until she starts brutally killing pigeons and breaking ankles of other children, where we start to get a hint that not everything is as it seems...
And oh boy, is everything not as it seems. The twist of Orphan reveals itself when Esther begins wiping make up from her face and popping out her grotty fake teeth, undressing to show herself as fully grown woman rather than the pre-teen she was posing as. A dangerous psychopath escaped from an Estonian psychiatric facility, she's really 33 years old: intent on seducing Jon and killing the Colemans before burning their house down for good measure.