19-year-old Paula Borchert is found dead in the Oder near Frankfurt. Inspector Olga Lenski and her colleague Adam Raczek take over the investigation. Paula had only recently been employed by Leo Heise as an au pair. Leo is a single father and lives with his two young children in the house of his parents Katarzyna Heise and Gerd Heise. Paula, who didn't take her au pair job very seriously, was very outgoing and had become friends with Milena and her boyfriend Marcin. During their research, the investigators came across an old case involving the Heise family: Julia Sikorska, Katarzyna's daughter and Gerd Heise's stepdaughter, disappeared 15 years ago. To this day there is no sign of life from her. Pawel Sikorski, Julia's biological father, has since suspected Gerd Heise of sexually assaulting Julia. Olga and Adam have to clarify whether Julia Sikorska's disappearance is related to the death of Paula Borchert.