The expulsion of the devil from my best friend

1988. Two girlfriends - Abby and Gretchen, familiar from school, study at the university. At the next student party, Gretchen disappears in the forest, but, having returned, assures that nothing happened to her, she just got lost. After that, her behavior changes dramatically - from a friendly, albeit closed, she becomes irritable and gloomy, and inexplicable phenomena are increasingly taking place next to her. Trying to find out what is happening, Abby begins to suspect that her friend is obsessed with demonic forces. Soon, at first, innocent events grow into real bloody horror and the game is no longer a living, but to death. Only Abby does not yet know that sometimes exorcism can be worse than any obsession