When the body of Ulrica Andersson, who has been missing for seven years, is pulled out of the Wandse Channel, a case comes to light that District Attorney Mehlhorn had once argued and lost. He was convinced that the husband, Gunnar Andersson, had killed his wife because she wanted to leave him. His children and his sister-in-law accused him of committing the murder. However, because they couldn’t find the body he was acquitted.
As Mehlhorn isn't allowed to officially investigate Andersson, he asks Bella Block to go undercover, win his confidence, and get him to confess. It’s the only possibility to reopen the case and prove the man is guilty.