The Blackcoat's Daughter is a haunting and underrated horror film from 2015 which ends on a shocking note. The Blackcoat's Daughter was written and directed by Osgood Perkins, son of genre legend Anthony Perkins (Psycho). Osgood started his filmmaking career as an actor, appearing in movies like Legally Blonde and Secretary. He later pivoted into writing screenplays, such as Bryan Cranston thriller Cold Comes The Night.
He made his directing debut with The Blackcoat's Daughter, which tells the story of two Catholic schoolgirls who get stuck in their boarding school and learn the nuns looking after them might be Satanists. The movie was greeted with strong reviews, praising the lead performances and the film's rich, bleak atmosphere. Perkins would follow up with the Netflix movie I Am the Pretty Thing That Lives in the House. Ruth Wilson (Luther) stars as a live-in nurse looking after a famed horror author suffering from dementia, who begins to suspect there might be a ghostly presence in the house with them.
The Blackcoat's Daughter sits right next to recent horror movies like Hereditary which function as powerful dramas, in addition to being scary as hell. The movie is split between two stories, with one plot following schoolgirls Kat and Rose, while another follows Joan, played by Emma Roberts (American Horror Story).
The Kat / Rose Storyline
The narrative cuts back and forth between those two stories without making their connection clear initially. Kat (Kiernan Shipka) and Rose, played by Lucy Boynton (Bohemian Rhapsody), are left at school together when their parents fail to pick them up, and Rose later tells Kat the nuns at the school are rumored to worship Satan. Rose is later disturbed to see Kat kneeling by the school's lit boiler and she starts to act in other bizarre ways. Kat also appears to have a premonition of her parent's death in a car crash, and later receives a phone call from a voice telling her to kill everyone at the school.
Kat proceeds to brutally murder the nuns and also kills Rose when she finds their bodies. Kat brings their decapitated heads to the boiler room and yells "Hail Satan!" That's when she's discovered by the headmaster and a police officer, who shoots her when refuses to drop a knife. In the hospital, a priest visits Kat and performs an exorcism, and when she gets a glimpse of the expelled demon she begs it not to leave, but it does.
The Joan Storyline
Joan is a young woman who escapes from a mental hospital and is later offered a ride by Rose's parents, played by Lauren Holly and James Remar (Dexter). The way the film presents the story, it seems Rose's parents are heading to pick her up, but it's later discovered Joan's plotline is set years later after Rose's murder. It turns out "Joan" is actually Kat and when they later drive by the abandoned academy, she asks Rose's parents to stop; "Joan" then murders Rose's parents and decapitates them. After applying some make-up, she takes her offerings to the boiler room to be reunited with her demonic friend, but the boiler is totally cold. Joan/Kat is last seen exiting the academy, sobbing in despair.
The Blackcoat's Daughter is ultimately about a young girl who willingly gives herself over to demonic possession so she won't be alone anymore. Despite being willing to kill for her "friend," even the demon ends up leaving her, and the movie ends with "Joan" utterly alone. There's also the question of if the demon exists or if its just a figment of Kat's imagination, but that's left up to viewers to decide. The fact she ends up traveling with Rose's parents years later makes it feels like other forces are at work, however.