I'm driving around Pakistan's largest city and financial capital, Karachi, with the mayor, Syed Kamal, who tells me that Islamists have penetrated th slums of this crucial port metropolis, pop 17 million, and may threaten its future.

We ride in an SUV preceded and flanked by police vans with a gunner poking his head through the roofs and two other shooters looking backwards out of the van. We pass by the highway overpass where the late Benazir Bhutto's convoy was blown up in Dec. 2007, shortly before she was assasinated in Islamabad. We drive by the radical religious school outside which Danny Pearl's body was dumped.

What's most scary is two things: first, there are 3500 such radical schools or madrassas, where young boys are closeted away until teenagerhood and brainwashed with radical versions of Islam. Many of them have been painted pink, in sympathy with the Red Mosque, a hotbed for radical preachers in Islamabad which was razed a couple of years ago but has now reopened. 

Second, there are mammoth slums in this city, into which refugees from Pakistan's Pashtun tribal areas have poured, and the mayor believes they contain sleeper Taliban cells that could be triggered to shut down the city, through which pour the supplies that travel by road to U.S. troops to Afghanistan. Heroin from Afghanistan,  also pours out of this port, he says, and Pakistan's strange police system - which leaves mayors without control over their security forces - allows this outflow to proceed unchecked.