One day in March, 1991, a burly, round-faced man with a thick, black beard appeared at the door of Mohammed Yuhana bin Hamidun's house in the village of Sungei Manggis, an hour's drive northeast of Kuala Lumpur. The stranger was dressed in a long Pakistani-style shirt, travel-stained trousers and opened-toed rubber sandals. Perched on his head was a black songkok, the distinctive Indonesian pillbox hat. He was carrying a plastic bag full of used clothes. Beside him stood a woman in a full Arabian-style black burka; only her eyes were visible behind thick glasses.

The man "stood outside my house and said, 'Assalammu'alaikum (the peace of Allah be with you,)' in a soft and pleasant voice. He looked so unassuming," says Mohammed of his first encounter with Riduan Isamuddin, better known as Hambali, the 36-year-old cleric now wanted by the U.S. and four Southeast Asian countries as the terrorist mastermind of the Asian operations of Osama bin Laden's al-Qaeda network and the guiding force for the past decade of most of the major acts of Asian terrorism.

Hambali had come to Sungei Manggis to rent one of a dozen wooden shacks that Mohammed built behind his own house and still lets out to Indonesian migrant workers for about $25 per month. The woman with him was his wife, Noralwizah Lee, a Chinese Malaysian from Sabah who converted to Islam. There were no protracted negotiations; the landlord wasn't picky about his tenants. "He said (former President) Suharto was after him for being an Islamic preacher," Mohammed recalls. "I told him, 'No arms, no havoc in my place. Pay the rent, you stay. I don't want to know anything more about you or other Indonesian migrants.'" He got his wish. For the next 10 years, Hambali kept a polite but firm distance from Mohammed and his family. Despite the steaming heat and suffocating lack of wind, the preacher and his wife rarely ventured out of the wooden shack; their door was always closed.

There was much to keep secret. Police in several countries and former associates say that grimy shack, with its constant swarms of mosquitoes, rough concrete floors and hole-in-the-ground toilet, was the center of operations from which Hambali plotted a breathtaking campaign of international terror. He has been linked to bank robberies and a political assassination in Malaysia and bombings that killed scores in Indonesia and the Philippines; authorities say he also raised funds, bought arms and recruited fighters for a jihad against Indonesian and Filipino Christians. Then there were the campaigns that failed to materialize, but sometimes came frighteningly close—like an abortive 1995 scheme to plant bombs on 12 U.S. airliners, or the plan to detonate seven huge car-bombs in Singapore earlier this year. And amidst all this, also, Hambali was the chief Southeast Asian representative and logistical coordinator for al-Qaeda. Police say he organized travel itineraries, accommodation and welcome dinners for two of the Sept. 11 hijackers and a suspect in the bombing of the U.S.S. Cole, and met with Zacarias Moussaoui, the so-called 20th hijacker now in a Virginia jail.

Unless he is captured and decides to speak out, it may never be possible to isolate exactly what combination of character and circumstance drove a man like Hambali, the son of a respectable Sundanese family of farmers and Islamic scholars, to dedicate his every waking moment for most of the past decade to a bloody struggle against those he sees as the enemies of Islam. But a close examination of his life yields vivid insight into how he accomplished so much—and what he might yet attempt. In a wide range of interviews conducted by TIME with police and government officials, relatives and former associates, Hambali emerges as a formidable figure, a meticulous, patient plotter, capable, when necessary, of taking massive risks when brewing commensurately destructive schemes. Hambali was also highly secretive, using his pious peasant demeanor as a cloak of invisibility. But that public timidity hid a personal magnetism the preacher deployed in private with devastating effect to manipulate followers. At Hambali's core was a calculating ruthlessness that allowed him to regularly dispatch those disciples on missions that would result not only in scores of victims but also in their own deaths.

MORE >>