Set in 1988, Abby and Gretchen have been inseparable since elementary school. When a misguided night of skinny-dipping takes a dark turn, Gretchen starts behaving strangely, prompting Abby to fear that she might be possessed. Determined to rescue her friend, Abby enlists the help of unexpected companions for a daring exorcism. As they confront supernatural forces, the strength of their friendship is put to the ultimate test. Can their bond withstand the evil that threatens to tear them apart?