Brakebills University is a secret institution specializing in magic. There, amidst an unorthodox education of spellcasting, a group of twenty-something friends soon discover that a magical fantasy world they read about as children is all too real— and poses grave danger to humanity.

Dawn is an active member of her high-school chastity club but, when she meets Tobey, nature takes its course, and the pair answer the call. They suddenly learn she is a living example of the vagina dentata myth, when the encounter takes a grisly turn.