Sauerland, autumn 1995: In the middle of the forest on the Wilzenberg, a walker finds the body of high school graduate Sonja Risse. However, the fact that the killer left a music box with the lullaby "Hush Little Baby" at the crime scene does not lead to a clear solving. 25 years later, the investigative journalist Stefanie Schneider, known as "Mütze", made a surprising discovery in Cologne. In a disused multi-storey car park, she films an undressed corpse of a man with a music box running next to it! When her colleague Jan Römer, who reported on the spectacular Sonja case as a young journalist in 1995, recognizes the melody from back then, he immediately believes there is a connection. He goes to Wilzenberg with his ambitious colleague to interview Sonja's mother Maria, her former teacher Waldheim and her best friends. The more the journalists compile, the clearer the contradictions and gaps that the investigators should have noticed at the time.
Veteran defense attorney Konrad Biegler accepts the defense of a man accused of kidnapping a young girl. At the trial he must face the tenacious police inspector Peter Nadler.