Though it was technically released second, Oz Perkins' first feature was The Blackcoat's Daughter, originally titled February, which premiered at TIFF in 2015 before a weirdly delayed release that pushed its wide release to 2017. Usually, delayed releases are bad news, especially for horror movies, but The Blackcoat's Daughter is great.
Told in three distinct chapters, it begins with two girls, Kat (Kiernan Shipka) and Rose (Lucy Boynton), who are stuck at their Catholic boarding school over the holidays for two very different reasons: Rose has lied to her parents so that they'd come a few days later so she can deal with a pregnancy scare, while Kat wonders if her parents have died on their way to get her after waking from what could be a prophetic dream of their car in pieces on a snowy road.
Meanwhile, a young woman named Joan (Emma Roberts) is picked up by a nice older couple as she's hitchhiking to the Catholic school's small town. As these things tend to happen, one of the girls starts talking to an evil entity residing in the bowels of the school, and seems to become possessed by a demonic force. It doesn't get any better from there; it ends on a pretty gruesome note, with an unexpected tinge of melancholy that turns your expectations of a demon possession movie on their head.