The Underworld (Fallen Star‪)‬

Gemma thought that her mind was gone, but she was wrong. And now she is left trying to figure out the truth of what Stephan is planning to do with her and the star, before it's too late. But finding out the truth is hard, especially since Gemma doesn't know who she can trust. There may be only one person who Gemma can turn to for answers, but that means having to go to the one place no one wants to go—the Underworld.