In a mysterious vault below the mountain of corpses, the police units not only discover more bones, but also a water glass 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 does not want to believe that he is no longer alive and now hopes to have found proof of this. She asks Adrian Demko for support. Adrian has been in a wheelchair since a terrible accident in her youth, in which 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 the two to a mysterious building in the border area - there an assassination attempt is carried out on Maggie.

Maggie was right: Kai is alive. The siblings hide together in the abandoned forest hut. Kai's confession that he has killed a lot of people upsets Maggie, as does his explanation, which seems almost unimaginable. After an attempted murder, both are in constant danger. Maggie turns to Voit - without revealing to him that her brother is alive or revealing anything about his involvement in the series of crimes. Meanwhile, Voit's colleague Zajak deciphers a mysterious document that the survivor from the mountain of corpses left behind before his death. On the Polish side, the student Ilona makes a scary discovery. Something is wrong in the isolated boarding school for street children and runaways. Blood donations are mandatory, girls disappear and scary men come and go.