On July 7, 2005, four bombs went off on London's transport network within an hour, killing 52 people and injuring more than 700, the first suicide attack carried out on British soil by attackers who turned out to be homegrown, ordinary young British men. The film follows the researchers who have spent careers trying to explain that fact. Ariel Merari of Tel Aviv University interviewed the families and friends of bombers, along with attackers who were caught before detonating, hunting for a distinct personality profile, only to find that suicide bombers show no consistent signs of mental illness or psychological abnormality. Forensic psychiatrist and former CIA case officer Marc Sageman takes a different route, mapping how the 9/11 hijacking cell actually formed and noticing that its leaders had all joined Al Qaeda while living abroad, away from family and community. Between the two approaches, the film builds a picture of radicalization as a social and group process rather than an individual pathology, with the July 7 attacks as its central, unresolved case study.