On a hot summer's day in 1996 a plane carrying Osama bin Laden and a few friends and family landed just outside the eastern Afghan city of Jalalabad. The Saudi-born Islamic activist had little equipment, few followers and minimal local support. Yet within five years he had built an organization that was to carry out the most shocking and devastating terrorist attack in history. In Arabic, the term "Al-Qaeda" is an abstract noun meaning resource, network or base. In the West, it symbolizes a great threat to global security. Though its Afghan training camps have now been reduced to dust, no one believes that al-Qaeda was destroyed with them. But what is al-Qaeda? Is it a disciplined, motivated, structured terrorist organization led by a single criminal mastermind or no more than an idea, a language in which angry young Muslim men can articulate their rage? Bin Laden's aim to provoke conflict between militant Islam and the West appears closer to fulfilment than ever. But is al-Qaeda the catalyst of this conflict, or merely a symbol of it? This is an investigation of the al-Qaeda phenomenon by a recognized expert on the subject.