Three and a half years after the Madrid massacre, the judicial and police investigation explains in detail how it was carried out, but hardly touches on the why. What led a religious fanatic – “The Tunisian” – and a drug dealer from Madrid – “The Chinese” – both with more than ten years of residence in Spain, to organize, lead, and perpetrate the slaughter? How could two men from such different worlds come together? Was this the decisive connection for the extremist plans? Why and how did they become so radically radicalized? What were their lives like, their environment, the key events in their biographies, their feelings towards their neighbors at different stages of their lives? How did they manage to organize? In what way were they serving Al-Qaeda? Justin Webster investigated the terrorists’ surroundings for two and a half years to try to answer these questions and present the answers in the form of a complex, yet clear, forceful, and revealing story for any kind of audience. For the first time, close relatives, friends, and acquaintances of the two terrorist leaders speak in depth. It is a story told by eyewitnesses and people who had direct contact with them at crucial moments. The narrative of events also includes interventions from the top officials of the criminal investigation, prosecutors, experts, and members of the Muslim community. Certain moments of the trial also help to uncover aspects of the story. The documentary pays special attention to those who, after an attack, never disappear: the victims.