Thirteen-year-old Olly Stephens left home for the final time on a Sunday afternoon in January 2021, telling his parents he was meeting a friend nearby. Fifteen minutes later, he had been murdered. Lured out by a teenage girl and stabbed to death by two teenage boys she had met online, the entire attack was planned on social media and triggered by a dispute on a chat group. With exclusive access to Olly's parents Amanda and Stuart, Panorama reporter Marianna Spring investigates the violent and disturbing world their son had been exposed to online and follows their campaign for tighter regulations on harmful content.