A young woman's body is discovered in a lake, initiating a complex investigation into her identity and her killer. Detective Martin Beck is tasked with solving the murder of a woman known only as Roseanna, whose body is found in Lake Vattern. With no immediate clues to her identity or motive, Beck must piece together the life of this free-spirited traveler to uncover the truth. The investigation becomes a deep dive into the victim's past and the psychology of a murderer with a peculiar sense of justice.

The first novel in the Martin Beck series, Roseanna establishes the series' reputation for realistic police procedurals and complex character development. Critics have noted its meticulous attention to detail in depicting the investigative process and its nuanced portrayal of both the victim and the detective. The book is recognized for its contribution to the Scandinavian crime fiction genre, offering a stark and compelling look at a murder investigation. It sets a strong foundation for the subsequent novels in the Martin Beck series.