The large LKA contingent is searching for a serial killer in Krewlow and hopes to get a clue from the only survivor found on the pile of corpses. However, the seriously injured man is unresponsive. For the village doctor Frank Seeger, it is clear that "Pulver-Paul" is behind the bloody deeds. The gun-crazy hermit is holed up on his farm and obsessively believes he has to defend himself against overpowering enemies. When Roland Voit and Stanislaw Zajak want to interrogate him, a life-threatening confrontation ensues. Meanwhile, Maggie is staying with Adrian Demko, her childhood friend who is in a wheelchair. She is convinced that the key to the Oderbruch serial murders lies in their shared past.

In a mysterious vault beneath the pile of corpses, the police units discover not only more bones, but also a jar of water with leeches. The seemingly insignificant find awakens the memory of Kai, Maggie's missing brother, in Roland Voit and Maggie Kring. Kai was an extraordinary, mysterious boy. Maggie simply cannot and will not believe that he is no longer alive and now hopes to have found proof of this. She asks Adrian Demko for help. Adrian has been in a wheelchair since a terrible accident in their youth, when an unexploded bomb from the Second World War exploded. He instructs his carer Marek Gorski to accompany Maggie on a trip across the border to Poland. The trail leads them to a mysterious building in the border area - where Maggie is assassinated.

Poland, summer 1990: ten-year-old Kai has been taken to safety by his mother Minna to stay with Polish friends. His father Arthur wants to kill him because he suspects that Kai has a sinister tendency. His sister Maggie fearlessly stands up for Kai and has to protect him from other children. A fight breaks out on the way to school, in which the leader Conradi is seriously injured and Maggie is knocked unconscious. Kai swears to his father that he will never tell Maggie the truth about himself. A sinister man also knows that the introverted boy is special. He seeks Kai out and offers him the chance to live with his "real" family.

SoKo Krewlow is on the hunt for Marek Gorski, who has gone into hiding, but a deadly trap awaits the officers in his trailer. Meanwhile, mysterious men have taken control of the Polish boarding school. Pupil Ilona fears for her life. On the run, she discovers a mysterious prisoner. He promises to help if Ilona frees him. Roland Voit is certain: there must be more than one perpetrator! When Gorski demands money from Demko for his escape, the police team drives to a remote drop-off point. However, Maggie Kring and Voit see through the ruse. A fight for life and death begins with the "Great Hunter", in which Maggie outgrows herself - and makes a fatal decision.