Despite being a self-professed science geek, high school freshman Camilla Mitchell has had a secret imaginary friend for years. It comes as quite a shock when said friend, Emma, accidentally drags her into a dimension full of hostile telepathic creatures. Cam's friends, her brother, Oliver, and her mother, Kathryn, work furiously to solve her disappearance and bring her home. Other members of their small Minnesota town disappear, one after the other, including Lizzy Becker's best friend, who is ripped from her arms. Lizzy badgers loner Oliver into working with her to rescue their missing loved ones. They discover a bridge between the two worldsa bridge that allows the hostile creatures from Cam's newly-discovered dimension into ours. If there's a bridge, there's a way to rescue the people taken. Right?