Vanished. Number 4 in series

For Seattle investigator Harper Blaine, her own case may prove the most difficult to solve. Why did she - as opposed to others with near-death experiences - become a Greywalker? When Harper begins digging into her own past, she unearths some unpleasant truths about her father's early death as well as a mysterious puzzle. She sets out to find his ghost but encounters only a void where he should be, leaving her with more unanswered questions.
Before she can continue her search, Harper gets an offer she can't refuse to go to London and pursue an investigation on behalf of some very demanding vampires. But there are unpleasant surprises waiting for her, and Harper soon discovers her present trouble in England is entangled with her dark past back in Seattle - and her ultimate destiny as a Greywalker.