Single parent Mona Doermer travels to the Baltic Sea with her two children Tom and Marlen. The mentally unstable mother and the children, which are alarmingly mature for their age, form a strange team that many in the coastal town notice – including the young Commissioner Greta. When little Marlen mysteriously disappears, there is great excitement. Greta, who feels strangely connected to Mona, does everything she can to find the missing girl and to discover the dark secret of the mysterious stranger.