Receiving a sealed bottle with a years-old plea for help by two young victims imprisoned in a boathouse by the sea, Detective Carl Morck follows leads to a desperate woman trapped in a brutal marriage to a man who keeps her in isolation and hides deadly secrets.

"The newspaper refers to her only as Victim 2117-the two thousand one hundred and seventeenth refugee to die in the Mediterranean Sea. But to three people, the unnamed victim is so much more, and the death sets off a chain of events that throws Department Q, Copenhagen's cold cases division led by Detective Carl Mørck, into a deeply dangerous-and deeply personal-case. A case that not only reveals dark secrets about the past, but has deadly implications...

Detective Carl Mr̜ck investigates the twenty-year-old murders of a brother and sister whose confessed killer may actually be innocent, a case with ties to a homeless woman and powerful adversaries.