Former head of Department Q Carl Mørck has retired. So when he comes across a disturbing audio recording, he turns it over to his former colleagues, who are struggling to keep the old department up and running on their own. That is until a new transfer unexpectedly arrives --- Helena Henry, a Frenchwoman who may also have secrets of her own. When the team realizes that the audio recording might shed new light on a murder-suicide case from years earlier, suddenly everything they thought they knew is called into question. Meanwhile, a spurt of seemingly random violence leads the Department Q team to investigate a possible connection to a different long-ago dark and sinister event, one that someone has never forgotten.