A DEADLY PUZZLE

The bookshop on Bude Street never opened for business last week. The sign on the whitewashed storefront says IQRA THE LEARNING CENTRE, but Muslim neighbors in the trash-strewn south Leeds district of Beeston say the place is almost always closed. Some don't think it's a proper bookshop at all. They say that the young men who frequented the place were running a radical Islamist indoctrination center. "I don't know what they were trying to do," said a local schoolteacher who was afraid to be quoted by name, "but they took a lot of young, free people who were clubbing and dancing, and they changed them."

On Friday police raided the shop. They didn't say whether they found anything suspicious, and the owner could not be reached for comment. But no one doubted what the searchers wanted: evidence in the four coordinated rush-hour bombings that killed at least 55 bus and subway riders in London on the morning of July 7. The bookstore's neighborhood was once home to three of the four suicide bombers. Mohammed Sidique Khan lived a block away on Stratford Street when he was a boy, before his family moved to another neighborhood nearby. Shahzad Tanweer used to live just around the corner. Hasib Hussain lived minutes away. They all knew each other.

Beeston's residents seem as baffled as anyone else by what could possibly have transformed the local boys into terrorists. Investigators on four continents are now urgently trying to answer the question. They're increasingly convinced that the London bombers could not have planned or carried out their bloody mission without guidance from at least one trained terrorist--a "skill-set operative," in the jargon of counterterror experts. As evidence continued to pile up last week, investigators found it increasingly plausible that Al Qaeda might have had a direct hand in the bombings. "What we expect to find at some stage is that there is a clear Al Qaeda link, a clear Al Qaeda approach," said Metropolitan Police Commissioner Ian Blair.

British and American officials close to the inquiry (they can't be named for fear of compromising the investigation) say that as far as they can tell, none of the four ever attracted serious attention from British police or intelligence agents who track Islamic extremists. Yet two of the suspected bombers appear to have had at least tangential connections to terror suspects from an earlier case. The most mysterious member of the bombers' group has been identified by British investigators as Germaine Lindsay, 19, a Jamaican-born British citizen and Muslim convert who has lived both in Leeds and in the town of Aylesbury, roughly 170 miles away. Some investigators now think he may have been the team leader. How he might have joined up with the others is still unclear.

Some American officials, who render the Jamaican bomber's name as Jermaine Maurice Lindsay, say he was on a list of some 2,000 names collected last year in connection with Operation Crevice, a British and Pakistani joint police action aimed at foiling an alleged terror plot. It appears that Lindsay had contact with someone under scrutiny in the case, which concerned a scheme to blow up London's Heathrow airport or some other target of similar magnitude. But the Jamaican, who American investigators say visited his mother in Cleveland more than once during the 1990s, was never listed as a major terror suspect, and some British officials deny they ever had him in their sights. Investigators say Mohammed Sidique Khan's name also surfaced in the Operation Crevice inquiry, which ended with the arrest of eight British-born ethnic Pakistanis. (Those eight appear to be in custody, awaiting trial, although Britain's restrictive press laws have circumscribed media coverage of the story.)

Lindsay's alleged partners were a mixed bunch. Khan, 30, worked with special-needs kids at Hillside Primary School and was the married father of an 8-month-old daughter. "He was a nice bloke," said Fred Dibner, 35, clutching a tabloid newspaper with Khan's photo on the front page and gently leading his tearful 9-year-old son out of the school gates. "He helped Joe catch up after he missed six months of school." People liked 22-year-old Tanweer as well, says Abbas Hanif, a regular customer at the family-owned fish-and-chips shop where Tanweer worked as a counterman. "He was a nice guy, peaceful," says Hanif. "He liked sports." Hussain, 18, was a successful business student at a local vocational school. Neighbors said he once had a wild streak but became more disciplined after a trip to Pakistan a couple of years ago.