Underground, by Kat Richardson, is the third novel in the Greywalker series.
After a near-death experience, Private Investigator Harper Blaine now has the ability to move between this world and the next. A place called the Grey. When her friend Quinton asks her to investigate a serial killer, Harper soon realizes that this is no ordinary killer. It’s a monster from old lore. And with her unique abilities, Harper is the only one who can hunt it down.
With history and lore tied to Seattle’s underground, this story is rich with ominous descriptives and suspense. Harper must deal with ghosts and zombies, which begin to interfere with her personal life. Shocking revelations, intense suspense, unique paranormal characters, and a mystery that keeps you guessing gives this urban fantasy more than its share of fun thrills. This series has continued to improve with each installment.