This feature documentary tells the inside story behind the hunt for ISIS poster boy "Jihadi John" by the US and British military and intelligence services. It interrogates the twisted worldview espoused by ISIS - the richest and most notorious Islamist terrorist organisation in history - and its propaganda machine which was operated by "Jihadi millennials" who turned social media sites such as Twitter and YouTube into recruitment platforms. This is the definitive story about the formation and collapse of ISIS as a "state", told through extraordinary first-hand accounts of key counter-terrorism and intelligence officials who identified "Jihadi John" as British terrorist Mohammed Emwazi - and ultimately killed him. The film explores the shattered lives, emotional and psychological turmoil of the family members whose relatives were barbarically murdered by Emwazi. It also projects the astonishingly self-critical evaluations by CIA, Scotland Yard, and Pentagon officials who expose their own failures in the fight against ISIS and why the organisation was allowed to exist and spread its poisonous ideology in the first place. We also hear from former hostages of Jihadi John who are desperate for justice, and the voices of Muslim community leaders who worked with parents whose radicalized children fled places such as the US and Britain to join ISIS on the battlefields of Syria and Iraq.