A series of mysterious disappearances in 2006 are eerily connected to the same institution.

Two workmen make an alarming discovery in an older Copenhagen apartment: hidden behind a false wall are three mummified corpses, sitting around a dining table with one empty seat left. The case quickly ends up on the desk of Detective Superintendent CARL MØRCK and his assistant, ASSAD, and it is up to them to figure out, who the mummies are as well as who the fourth seat is meant for. Carl and Assad put all effort in to finding the tenant of the apartment and they end up finding clues tracing back to the notorious institution for 'wayward' girls on the island of Sprogø, where extreme neglect and medical experiments in forced sterilization are a part of everyday life. Even though the horrors of Sprogø are a closed chapter in Danish history, there are now people claiming the experiments have continued to go on up until today. Carl and Assad start a race against time to prevent new murders and attacks from happening.

It's been five years since the first success of the Department Q in Kvinden i buret (2013), and only two short years since the hunt for the serial killer in Flaskepost fra P (2016), and now, the division is facing imminent radical change. This time, two separate incidents--the gruesome discovery of a tortured trio of missing people and the unaccountable disappearance of a prostitute--set in motion the reopening of a twelve-year-old cold case that switches back and forth between the murky past of Sprogø Island and the present. With Rose searching for vital information, gruff Detective Carl Mørck and his invaluable partner Assad follow a faint trail of clues in a dangerous, opaque mystery of lost innocence, sinister master plans, permanently damaged women, and hate-driven vigilante justice. Is revenge, indeed, a dish best served cold?—Nick Riganas