A 41-year-old woman is reported missing, and when the police unravel her digital footprints, they discover she has been stalked for months. An unidentified perpetrator has been playing a game of hide and seek, surveilling her while sending her not only images and videos but also a seemingly innocent nursery rhyme-style counting song.

When the woman is later found murdered, it becomes evident that this case is linked to a similar, unsolved case of a 17-year-old high school student who was found murdered two years ago. But what is the connection between the two victims? And when will the perpetrator begin to "play" hide and seek again?

Detective Hess and Thulin reunite as they race against time to catch the perpetrator playing this disturbing game in the gloomy mists of Copenhagen's suburbs. As more victims are drawn into the deadly game and the body count rises, the duo must stop the killer before more lives are lost.