In the 1990s, a series of gruesome killings - later known as the acid barrel murders - would come to haunt Germany’s collective memory. Yet for a long time, no one knew the woman who brought the killer to justice. Marianne Atzeroth-Freier was one of the first female detectives in the Hamburg homicide division. While investigating a missing person case, she uncovered several inconsistencies. When she approached her male colleagues, no one within the police force was willing to listen. Undeterred, she continued the investigation on her own...