Mahmood the smuggler nods up the desert highway toward Iran's mountainous border with Pakistan and Afghanistan. He suspects that many of his Arab passengers are members of al-Qaeda fleeing the authorities. "I don't care who you are. Even if you're a criminal, I'll take you, as long as you've got the money," he says, revving up his Toyota.
Hunted in Afghanistan and Pakistan, al-Qaeda terrorists are slipping into Iran in droves, often with the aid of smugglers like Mahmood. Washington believes that several al-Qaeda leaders, including security chief Saif al-Adil, are hiding in that country. Iran counters that it's impossible to...