On May 7, 2001, nine-year-old Peggy Knobloch disappears. A Germany-wide and international search for the child begins. But the police can't find any trace of Peggy. Her body was found on July 2, 2016. Peggy Knobloch's disappearance remains a mystery and is one of the most famous criminal cases in Germany. The case is reconstructed in detail in this documentary series.