The Night Season by Chelsea Cain

The Willamette River in Portland, Oregon is swelling and police detective Archie Sheridan is on the trail of a serial killer who is poisoning people and then throwing their bodies into the river. Archie's partner, Henry, is himself attacked. He barely survives, but his prognosis is uncertain. Meanwhile, reporter Susan Ward recently wrote a story about a skeleton that was found in an area that was wiped out in a flood in 1948. She is also working on a story about the recent murders. Archie's and Susan's paths intersect often and they work together to try and uncover the identity of the killer before he sadistically murders again. All the while, they deal with the chaos around Portland as it floods. In this fourth thriller featuring Archie and Susan, Cain is able to write a good story without the presence of a series regular, serial killer Gretchen Lowell. In fact, it's quite refreshing for that story to be in the background.