Labyrinth. Number 5 in series

Just back from London, Harper picked up some new skills while she was away. But instead of taking the time to hone them, she'd rather focus on what's important. Like finding the two-bit perp who 'killed' her. She's convinced he's a valuable clue in the puzzle of her past and her missing father, as well as a key to figuring out who's trying to manipulate her powers and why. There's just one problem.
Turns out the man who "killed" her was murdered himself while she was away. Lucky for Harper, she has an airtight alibi, but that doesn't mean the police are going to play nice. With Seattle's recent surge in violence - thanks to the vampires - she's already under suspicion. Which means Harper has to watch her step. Because finding the ghost of her 'killer' - and rescuing her father - will mean entering into the Grey.
And with her growing powers pulling her more deeply into that paranormal world, Harper's afraid she may not be able to come back out...