Detective Carl Mørck heads Department Q of the Copenhagen Police Department. Department Q, a sort of orphan division that investigates cold cases, is confined to a cramped basement and staffed with police oddballs, including Carl's invaluable assistants Assad and Rose.
Carl, who was gravely injured in an incident that killed one colleague and paralyzed another, prefers to laze around, drink coffee, nap, and avoid work. Thus, when Detective Christian Habersaat asks for assistance with a 17-year-old cold case involving the death of a beautiful girl named Alberte, Carl refuses. Habersaat, whose life was ruined by his obsession with the case, commits suicide the next day. Rose is horrified and bullies Carl into investigating Alberte's death.
Carl and his colleagues gather Habersaat's massive collection of 'Alberte files' and painstakingly go through them. They eventually find a poor, grainy photo of a man beside a van and expend great effort to discover who the man is and how he was connected to Alberte. During their inquiry the detectives speak to Habersaat's family and colleagues, and to Alberte's relatives, friends, and teachers. Many of these people are oddly hostile and uncooperative.
A parallel story line involves a nature-worship cult headed by a charismatic leader called Atu Abanshamash Dumuzi - a man who's oddly irresistible to women. This has unfortunate consequences because Atu's assistant Pirjo carries a huge, unrequited torch for him and will do anything to get rid of the competition.
For me, this book isn't as successful as previous books in the series. The plot is disjointed and Department Q's inquiries are too drawn out and tedious. I also feel that the characters aren't as engaging as usual. Assad - with his warm heart, confusion with idioms, crazy driving, and intuitive detective work - is still a fun, memorable character. Rose, however, doesn't exhibit her usual kooky, multiple personality traits and Carl's interactions with his friends, colleagues, ex-wife, and ex-stepson aren't as compelling as usual. Moreover, many of the ancillary characters are too self-centered or psychopathic to be sympathetic.
The book can be read as a standalone but readers unfamiliar with the previous books may be confused about some characters and situations. All in all this is a pretty good mystery with lots of unexpected twists. The story ends with a dramatic climax that leads to a satisfactory conclusion. I'd recommend the book to people who like mystery books, especially fans of Jussi Adler-Olsen.