On Friday, 26th November 2010, in the close-knit town of Bergamo, Letizia Ruggeri received a telephone call. It was Maura Gambirasio, a mother whose 13-year-old daughter Yara hadn't come home from the gym. Letizia, who spent years investigating mafia murders in Sicily, thought of her own daughter and promised she would find Yara.Three months later, Yara's body was tragically discovered - she had been attacked. With just one piece of DNA evidence to go on, Letizia started a hunt for a perpetrator that would take four years, 20,000 DNA samples, ingenuity and tenacity to find the identity of 'Unknown Male no 1'. It was a revelation that would unlock deep family secrets that still reverberated when the suspect was finally brought to trial.