When terror strikes, it always tears through the comforting screen of normality. One moment, midmorning shoppers and workers bustle along Nairobi's Haile Selassie Avenue at the downtown corner where a bronze eagle and a fluttering flag mark the five-story U.S. embassy. The next, the earth trembles as a thunderclap unleashes a mighty shock wave. Seconds later, black smoke plumes into the sky as the tarmac ignites, flashing fire to parked cars and passing buses. The blast shatters every window within a quarter-mile radius into lethal slivers, blows the bombproof doors off the embassy, sucks out ceilings and furniture and people, pancakes...

