Being a teenager can be hard, especially if you're Callie Catwell.

She already has plenty of worries in her life—a father struggling with anorexia, a friend with an abusive stepfather, an ex-boyfriend who won't let their relationship go, and questioning her sexuality and new feelings for her best friend— and that's not even taking into consideration the struggles that just come from growing up. Things suddenly take a strange turn when she sees a monster in the Lost Lake one morning. Finding that monster soon becomes an obsession, one that distracts her from the anxieties in her life. While she initially welcomes the distraction, Callie soon has to decide if she is ready to face her struggles or ruin her relationships with her family and friends—and the monster's strange magic—forever.