Pieter Vos, a detective with the Amsterdam police, is given cause to re-open the case when the girls disappear along with the nurse responsible for escorting them to a halfway house. When the nurse's corpse washes up on the beach at Marken, it becomes apparent that the institution holds the key to the investigation. And it seems that Vos's boss, De Groot, has something to hide which is relevant to the case.
Then, the case takes an unexpected turn when it becomes clear that someone is posing as Little Jo - Kim and Mia's other sister - who was supposedly murdered along with their parents ten years ago . . .