Underground (Greywalker)

Harper Blaine was your average small-time P.I. until she died - for two minutes. Now Harper is a Greywalker - walking the thin line between the living world and the paranormal realm. And she's discovering that her new abilities are landing her all sorts of "strange" cases.
Pioneer Square's homeless are turning up dead and mutilated, and zombies have been seen roaming the underground - the city buried beneath modern Seattle. When Harper's friend Quinton believes he may be implicated in the deaths, he persuades her to investigate. But the killer is no mere murderer - it is a creature of ancient legend. And Harper must deal with both the living and the dead to stop the monster and its masterunless they stop her first.