Gretchen Lowell, book 4: The Night Season
Chelsea Cain2011

Heavy rains have burst the banks of the Willamette River; several people have died in the furiously rising waters... but the latest victim didn't drown. She was killed before she went into the water. Soon, other victims are found, and Police Detective Archie Sheridan realizes that Portland has a new serial killer on its hands.

Reporter Susan Ward is on the story, but she's got other leads to chase, and some secrets can be too frightening for prying eyes. With Archie following a bizarre trail of evidence, and Susan close behind, the pair mus unearth the identity of a vicious murderer, and uncover the truth behind a mystery more than sixty years old...