Hidden Court. The Gatekeeper's Trials, #2

Hazel's tenure as Gatekeeper between the Summer Court and the human realm has barely begun and she's already stopped one attempted coup. But with no monarch in control of the Summer Court of Faerie, full-blown anarchy threatens to break out. Everyone wants a piece of the Gatekeeper -- in a literal sense, if they find out the explosive secret the Erlking left her with after his death. Worse, a notorious fae criminal has escaped jail, and in the process, kidnapped the only person who knows the identity of the next ruler of Summer.
Hazel's first task as Gatekeeper is to find both of them, and save the heir of Summer before the Courts fall into chaos. She has help in the form of her old mentor, Darrow, except he's here on a mission from his own Queen that puts Hazel in even more danger. As she closes in on the enemy, it becomes harder and harder for Hazel to keep her loved ones safe. Torn between promises old and new, Hazel is going to have to betray someone.
and her decision might well lead to the ruin of everything she's ever known.