Well before Umar Farouk Abdulmutallab disappeared into the rugged mountains of Yemen with an ominous goodbye to his father -- warning him that ''this is the last time you are going to hear from me,'' according to top Nigerian officials -- the tensions between the two pious men had already begun to show. Though his father's career in banking had brought great wealth, enough to finance a neighborhood mosque in the family name and hire a private imam at home, his cousins said the young Abdulmutallab openly condemned the profession as immoral for charging interest and lectured his father to quit. 'Anytime he came back on vacation' from studying abroad, said a cousin on the condition of anonymity because the family has forbidden contact with the news media, 'he would tell his father he needed to quit banking because it was un-Islamic.' Behind Abdulmutallab's journey from gifted student to terrorism suspect, accused of trying to bring down a plane headed to Detroit on Dec. 25 with explosives sewn into his underwear, is the struggle between father and son, between piety and radicalism, between an investment in this life and a disconnected young man's apparent longing for the next. It is a struggle within Islam itself, not just in the Middle East or in centers of jihadist ideology like London, but also here in Kaduna, the northern Nigerian city in which Abdulmutallab grew up and returned to on vacation. This is a place where the dividing line between devotion and extremism is often blurred, where Islamic police ensure that moral codes are obeyed, where scores were killed in religious violence incited by the Miss World contest in 2002 and where even a family as Westernized as Abdulmutallab's has had contact with local clerics espousing anti-Western and anti-Israeli ideals. 'Kaduna city has a long history of religious extremism and intolerance,' said a neighbor, Shehu Sani. 'For 30 years, there has been violence here. People like Farouk grew up in this atmosphere. I don't think all his radical ideas came from Yemen.' While it may be rare for a child of privilege like Abdulmutallab to embrace extremism, it is far from unprecedented, analysts say, bringing to mind some infamous cases. John Walker Lindh, the American captured as a fighter for the Taliban in northern Afghanistan, was the son of a lawyer and grew up in the gentle, moneyed suburbs of Marin County, Calif. Osama bin Laden's father was a staggeringly wealthy contractor in Saudi Arabia, while his second in command in al-Qaida, Ayman al-Zawahri, is a doctor who comes from a highly prestigious family in Egypt. And like Zawahri, some analysts say, Abdulmutallab shared another trait of some notable jihadists. 'He is alone and isolated,' Hani Nesira, a director at Al Mesbar Studies and Research Center who specializes in Islamic movements. 'These kind of individuals are usually different from their social surrounding and are unable to find themselves.' Moreover, they often come from families that may monitor educational performance but are removed from 'their moods and their psychological and intellectual inclinations,' Nesira added, enabling the lonely or depressed to seek belonging in 'a religious utopia,' sometimes a very radical one. 'THE REAL ISLAM' That kind of detachment from others and singular focus on Islam was a common thread in Abdulmutallab's life, according to family members, friends and classmates. It was evident long before he sent the kind of strident text messages to his father -- saying that he had found 'the real Islam' and that his family 'should just forget about him,' the cousin said -- that alarmed his father enough to warn American officials this November that Abdulmutallab was a security threat. 'He is a total teetotaler,' said Abdulmutallab's uncle by marriage, Mahmoon Baba-Ahmed, who runs a television station in Kaduna. 'He doesn't do what his peers used to do. He is always indoors reading his Quran.' While other rich children were going to parties, Abdulmutallab spent his visits home across the street, at the mosque financed by his father, Alhaji Umaru Mutallab, and bearing his grandfather's name, always in the front row. His piety was so pronounced that the young people around here mocked him for it, his neighbor said. It also set the stage for conflict within his own family, devout though it was. Along shady Ahman Pategi Road, an oasis of palms and mango trees in this dusty city, the security guards of the affluent Unguwan Sarki neighborhood know the story well. One evening the young Abdulmutallab brought out a plate with leftovers from the family dinner table -- his father's plate -- to give to one of the guards. His mother's rebuke over this breach of etiquette was voluble enough to reach the domestic workers; the young man's calm response was to cite a verse from the Quran on duties toward the less fortunate. 'He wasn't close to his father,' said Aminu Baba-Ahmed, a cousin by marriage. Ill will had simmered after the lonely young man, at 21, had expressed a desire to marry, the cousin said, but his parents blocked it, saying he did not yet have a master's degree. Increasingly, Abdulmutallab was close to nobody, according to those who know him here in Kaduna. The young man who as a teenager who had happily played basketball and PlayStation with his cousin had retreated into his faith. In Internet postings in 2005, when Abdulmutallab was a student at a British boarding school in neighboring Togo, he pondered his sense of isolation. 'I feel depressed and lonely,' he wrote. 'I do not know what to do. And then I think this loneliness leads me to other problems.' By 2007, as Abdulmutallab studied mechanical engineering at University College London, the transformation was deep. 'He had changed; he was saying 'Islam, Islam, Islam'; he was saying we should all try to change, and be more Islamic,' Aminu Baba-Ahmed recalled. Even in recent months, he said, the fun-loving boy he had known was chiding him about going to parties. 'I was really surprised,' Baba-Ahmed said. RACIALISM TAKES ROOT Radical politics had also firmly taken root. While in London, Abdulmutallab lived alone, according to a friend there, in a family property at 2 Mansfield St., an imposing white-pillared building in an upscale neighborhood near Regent's Park where Mercedes and Bentleys abound. Newspapers, neighbors and even some family members in Nigeria now blame this lack of supervision, a symptom of what they call the neglect among the Nigerian elite, for facilitating Abdulmutallab's slide toward extremism. His family may have reasonably assumed that Abdulmutallab's piety would stave off any profligacy, and it did, at least in the conventional sense. Instead, he took quite a different turn, attending prayers at London mosques under watch by British security services because of their radical links. Still, while he was seen to be 'reaching out' to known extremists and appearing on 'the periphery of other investigations' into radical suspects there, he was not considered a terrorist threat himself, according to a British counterintelligence official. For the inaugural lecture of the 'War on Terror Week' that Abdulmutallab helped organize as president of the college's Islamic society from 2006 to 2007, the group booked a large lecture hall. It was a full house, said Fabian De Fabiani, a student at the time who attended, with about 150 people. Some members of the society dressed in the orange jumpsuits similar to those of Guantanamo Bay detainees; they stood at the doors and handed out leaflets. Abdulmutallab was seated 'where the lecturer would usually sit,' De Fabiani said, 'very close' to Moazzam Begg, a former Guantanamo Bay detainee then in contact with Anwar al-Awlaki, the radical preacher whom officials say Abdulmutallab probably met in Yemen before setting off on his failed bombing attempt. In an interview, Begg acknowledged attending the event but said he did not recall meeting Abdulmutallab. 'When we sat down they played a video that opened with shots of the twin towers after they'd been hit, then moved on to images of mujahedeen fighting, firing rockets in Afghanistan,' De Fabiani said. 'It was quite tense in the theater, because I think lots of people were shocked by how extreme it was. It seemed to me like it was brainwashing, like they were trying to indoctrinate people.' There is a very big difference, of course, between religious devotion or radical politics and violence, and while 'many, many people start the journey' toward extremist Islam, only a 'small number' of people are committed to bloodshed, the British counterintelligence official said. Since the bombing attempt, newspaper editorials, psychologists and officials in Nigeria have suggested that Abdulmutallab was hardly Nigerian at all, that his ideas came from his time studying overseas. NO SHIELD FROM ISLAMIC FERVOR But as rich and shielded as Abdulmutallab's family was, it was not quarantined from the Islamic fervor that has led to outbreaks of violence in Kaduna. In 2002, Muslim youths rioted and clashed with Christians after a newspaper article suggested that the Prophet Muhammad might have been happy to choose his wife from among the Miss World contestants, who were set to compete 100 miles away in the capital, Abuja. Some 220 people were killed, and mobs burned 16 churches, nine mosques, 11 hotels and 189 houses, according to a local civil rights groups led by Abdulmutallab's neighbor, Sani. Though the violence did not touch the serene family compound, the radical views permeating society might well have. Abdulmutallab's family attends one of Kaduna's largest mosques, the Sultan Bello mosque, for Friday prayer and sermons, said the imam there. Anti-Western and anti-Israeli sermons are staples within its walls, said Nasir Abbas, a local human rights advocate who attends the mosque. 'You would hear about what Israel has been doing to Palestine, you would hear that, and also America's contributions to the Israelis,' Abbas said. In fact, at 'all of the mosques' in Kaduna it is possible to hear anti-Western preaching, he said. Abdulmutallab's father evidently did not share those views, since he was the first to report the danger presented by his son. Yet even Mutallab encountered people here like Imam Ibrahim Adam, who said he had been in the family home and had met with Abdulmutallab's father at 'religious gatherings' and meetings for a proposed Islamic bank, of which Mutallab is chairman of the board, according to the bank's Web site. 'Yemeni Muslims should have been the ones to attack America, not a Nigerian,' said the imam, although he carefully added that he did not personally support the attack. Exactly what drove Abdulmutallab's father to report his son is still a source of debate within the family. In telling the Americans, he 'acted on the dictates of his religion,' said the uncle, Baba-Ahmed. The father later viewed his son's arrest in much the same way. 'He summed it up with a verse from the Quran,' Baba-Ahmed recounted. ''This is a trial: your offspring can be a source of happiness and sadness.'' But the cousin who asked to remain anonymous had a more nuanced explanation for Mutallab's report. 'This is somebody who has investments in the Western world since before the boy was born,' the cousin said. 'He's got a 4 million pound house in London. Now the boy is jeopardizing everything.' While studying in Dubai last year, Abdulmutallab did not appear overly restless, doing better than average in his classes and quietly reading the Quran on the shuttle bus from student housing to campus each day, according to a classmate and the school director. But inwardly, he was apparently chafing against the secularism around him, and he argued with his father over the graduate business program in which he was enrolled before abruptly dropping out. 'His father wanted him to continue his studies,' said an Arab official with close ties to intelligence services in the Persian Gulf. 'He didn't want to. It wasn't the Arab world for him. It wasn't the Muslim world. That's when he got' really angry 'and went to Yemen without his dad's permission.' Abdulmutallab entered Yemen on Aug. 4, with a visa to resume his studies at the San'a Institute for the Arabic Language, where he had studied the language in 2004 and 2005. But this time his mind was elsewhere, and he offered excuses about why he was seldom in class. He said he had a throat infection and 'and was thinking of going to Dubai to check it out, and we said that there are hospitals here,' said an American classmate of his. 'He'd even leave class in the middle to go to pray at the mosque.' Investigators are now trying to piece together his movements, examining how he managed to slip out of sight after being driven to the airport on Sept. 21 with an exit visa. Yemeni officials have said he went to the remote, rugged mountains of Shabwa Province, where he met with 'al-Qaida elements' before leaving Dec. 4, a few weeks before his fateful journey to Detroit. After the disappearance, Abdulmutallab's father tried desperately to get him back. He enlisted one of his powerful friends, a retired national security adviser, to track his son down using the National Intelligence Agency, Nigeria's version of the CIA. But the new director of the agency did not go along with it, officials here said. 'The impression he had was, they were using the service to locate the prodigal son of a rich man, who was off enjoying himself somewhere,' said a top Nigerian security official. 'I don't think he did anything. He didn't have any idea about terrorism.' Since his son's arrest, Mutallab has remained out of public view. The father 'is extremely worried,' Baba-Ahmed said. 'Everybody is worried.' 