The Keeper of Lost Causes by Jussi Adler-Olsen 400 pp.
This is the first of the "Department Q" series by a popular Danish author. Carl MØrck, one time homicide detective has been assigned to a new department handling cold cases. MØrck suffers from PTSD since he was shot in an incident that killed another officer and paralyzed his partner and good friend. Now he is stuck in a basement office with files of cold cases and a Syrian refugee assistant who is efficient at some things, drives insanely, and is quite good at investigation while being a bit of a pest. They settle on investigating the disappearance of a politician five years before while the rest of the police department seeks the murderer of a bicyclist. The politician's disabled brother is the only possible witness to her disappearance but he does not communicate. MØrck's investigation alternates with the story of a woman imprisoned in a hostage situation. There is an ending but it is not a completely happy one. The story has a few confusing spots but I blame that on the translation from Danish. All in all, it's a good mystery/thriller. I listened to the downloaded audio book from Overdrive.