The story takes place in the 80s. Abby and Gretchen, best friends since fourth grade, have a highly overlapping interest in supernatural things. The calm and peaceful friendship changed after a naked swimming incident, and Gretchen began to become moody. Where Gretchen is, weird things keep happening... As strange coincidences and bizarre behaviors gradually accumulate, Abby realizes a possibility: there is a demon living inside her best friend Gretchen. Abby won't let anyone or anything stand between her and her best friend. With the help of some unlikely allies, Abby begins to seek a way to save Gretchen. Is the friendship between the two girls enough to defeat the demon in Gretchen?