A colonial upbringing

Khan's roots stretch back to the era of colonialism. As a 10-year-old he saw first-hand the violence that accompanied the end of British rule and the partition of the subcontinent, when he took a harrowing train ride through the desert border region of Khokhrapar to what would become independent Pakistan.

That ride - and what it symbolized - have apparently become central to his character. In Khan's beautiful stone house in the Margalla Hills of Islamabad, a main item of décor is a massive painting depicting the last train crossing into Pakistan before borders were sealed. Throughout his career his chauvinistic rhetoric and anti-Indian taunts have been a crucial reason for his appeal to the Pakistani masses.

"He is hard-core nationalist and a very ambitious person," says A.H. Nayyar, a physicist at Quaid-e-Azam University in Islamabad. "He is in for fame and money."

But neither is Khan an Islamist extremist of the sort suspected to be behind recent assassination attempts against President Musharraf. His wife is a Dutch national whose first name is Henny. Neither she nor their two daughters wear the traditional hijab, or veil. "He is not a fundamentalist . . . but he prays five times [a day] and is a religious person," says his biographer, Zahid Malik.

He is not a nuclear scientist per se, but a metallurgist. He did postgraduate work in Western Europe in the 1960s, and was then recruited to work at a uranium enrichment plant run by Urenco, a Dutch-British-German consortium.

The details of his return to Pakistan remain murky to this day. According to the account in Mr. Malik's biography, in 1974 Khan wrote Prime Minister Zulfikar Ali Bhutto offering his services to his country. In 1975, during a visit home, Khan visited Mr. Bhutto in his office, and agreed to his plea to return and help Pakistan develop nuclear technology. According to Malik's account, the prime minister then thumped his desk and cheerfully swore that he would now be able to trump India.

Western intelligence believes that Khan is something of a self-promoter. But they agree with Pakistani sources on one thing: Khan brought with him plans for Urenco enrichment technology.

In 1983 a Dutch court convicted Khan in absentia for attempted espionage. The conviction was later overturned on a technicality. Khan himself denies that Pakistan's centrifuge design was purloined, despite its similarity to Urenco work. "He's an extremely proud man and does not want to have the rest of the world believe that he got the centrifuges by stealing the designs," says Matthew Bunn, a nuclear expert at Harvard University.

As head of Pakistan's nuclear effort, Khan was not a technical genius but a managerial one, focusing his country's limited resources on one goal while craftily learning to ply the world market for needed parts and technology, both legally and on the black market.

National figure, international notoriety

After Pakistan detonated nuclear devices in 1998, his status as national hero was assured. But he's far from an international hero. Throughout his career Khan has complained about perceived Western hypocrisy about nuclear weapons and boasted of his ability to beat constraints. Western intelligence believes he has made some 13 trips to North Korea, for instance, in pursuit of a swap of nuclear technology for ballistic missiles. The UN's International Atomic Energy Agency is now investigating possible links between Pakistan and Iran after Tehran acknowledged using centrifuge designs that appear identical to early Pakistani models.

There are indications that Libya received Pakistani technology as well.

Officials say six suspects remain in custody. Among them are three scientists: former director general of the KRL, Mohammad Farooq, and two other close aides of Khan. At this writing, Khan has not been detained but his movement has been restricted and his Islamabad residence is under 24-hour watch.

Pakistani officials say it is possible that their nation's scientists might have engaged in weapons proliferation - on their own. Khan's daughter has said publicly that her father is being made a scapegoat.

"If half of this is true," says Michael Krepon, former director of the Henry L. Stimson Center, "it suggests a huge breakdown in [proliferation] oversight that must be repaired."