TIME:

Al-Qaeda terrorists came within 45 days of attacking the New York subway system with a lethal gas similar to that used in Nazi death camps. They were stopped not by any intelligence breakthrough, but by an order from Osama bin Laden’s deputy, Ayman Zawahiri. And the U.S. learned of the plot from a CIA mole inside al-Qaeda. . . .

The news left administration officials gathered in the White House with more questions than answers. Why was Ali cooperating? Why had Zawahiri called off the strike? Were the operatives planning to carry out the attack still in New York? “The CIA analysts attempted answers. Many of the questions were simply unanswerable.”

One man who could answer them was al-Ayeri — but he was killed in a gun battle between Saudi security forces and al Qaeda militants, who had launched a mini insurrection to coincide with the U.S. invasion of Iraq. Suskind quotes a CIA operative as questioning whether it was an accident that the Saudis had killed the kingpin who could expose a cell planning a chemical weapons attack inside the U.S. “The Saudis just shrugged,” the source tells Suskind. “They said their people got a little overzealous.”

Interesting.