The Heretics (2017)

Gloria is kidnapped by a cult that, under a locust moon, performs an occult ritual while wearing grotesque masks before committing suicide. Five years later, a traumatized Gloria is living with her mother, Ruth. Slowly recovering from her experience, Gloria attends a therapy group at her local church with her lover Joan. Joan tells Gloria she has something special planned for their anniversary the next day. However, Gloria is kidnapped by Thomas, a man whose face is hideously scarred by fire, and taken to a remote cabin in the countryside.

Joan launches an increasingly frenetic search for Gloria and pulls a knife on a man who is indifferent to Gloria's kidnapping. When a police officer learns of Joan's violent behaviour, he suspects that she was involved in Gloria's kidnapping, which leads her to kill both him and the inconvenient witness Ruth. Thomas tells Gloria that he was one of the cultists who had kidnapped her five years ago and that he was moved by her humanity, which caused him to abandon his beliefs on that night. He feigned suicide and stated that he kidnapped her to protect her from the remaining cultists, who intend to finish the ritual under the coming locust moon. The cultists believed that they had implanted the demon Abaddon, the "Taker of Souls", into Gloria's body and that it has been growing inside of her for the last five years.

Under the light of the locust moon, Gloria becomes seriously ill and begs Thomas to take her to a hospital. Both Thomas and Gloria experience visions of Abaddon while various occurrences suggest a malevolent supernatural force is present in the cabin. As Gloria begins to grow wings, Thomas starts to believe she really is turning into Abaddon and contemplates killing her before the transformation is complete. Joan is revealed to be the leader of the cult who kidnapped Gloria. Thomas tells Gloria that Joan is actually his sadistic sister Gwendolyn, who scarred him with fire. Gloria, whose appearance becomes increasingly inhuman as the metamorphosis progresses, starts to lose herself mentally and speaks in the voice of Abaddon, saying that she will kill Thomas first and take his soul to hell.

Gwendolyn learns from a witness that Gloria's kidnapper had a scarred face, which leads her to deduce that it was Thomas. Gwendolyn goes to the cabin (which belonged to their parents), knocks out Thomas, taunts a chained Gloria over her physical degeneration, and begins to perform an occult ritual. Thomas breaks free, kills Gwendolyn, and takes a seemingly dead Gloria outside under a rising sun. Gloria revives and attacks him, saying in the voice of Abaddon that she will take his soul to hell.