Together with a private team of investigators, the so-called core team, Bethge reopens his sister's case after his retirement, obtains all the files and manages to get into Becker's "secret" room again. There, even many years later, there were overlooked indications of a serious suspicion. Did his sister fall victim to a mysterious serial killer?

A new witness describes Jürgen Becker as a sadistic and unscrupulous seducer who tried to get money in every conceivable way. Anne Bach, together with Thomas Bethge, creates the image of a psychopathic serial killer who, since childhood, has tried to satisfy his experiences of powerlessness on his victims. Thomas Bethge once again looks at Jürgen Becker's farewell letters in search of the secret of his missing sister.