Between 1994 and 2000, Omar Nasiri worked as a secret agent for Europe's top foreign intelligence services-including France's DGSE (Direction Générale de la Sécurité Extérieure), and Britain's MI5 and MI6. From the netherworld of Islamist cells in Belgium, to the training camps of Afghanistan, to the radical mosques of London, he risked his life to defeat the emerging global network that the West would come to know as Al Qaeda. Now, for the first time, Nasiri shares the story of his life-a life balanced precariously between the world of Islamic jihadists and the spies who pursue them. As an Arab and a Muslim, he was able to infiltrate the rigidly controlled Afghan training camps, where he encountered men who would later be known as the most-wanted terrorists on earth: Ibn al-Sheikh al-Libi, Abu Zubayda, and Abu Khabab al-Masri. Sent back to Europe with instructions to form a sleeper cell, Nasiri became a conduit for messages going back and forth between Al Qaeda's top recruiter in Pakistan and London's radical cleric Abu Qatada.