The evening air was brisk, an overture for the approaching cold of winter, when a yellow and green cab stopped at a security gate on the south end of Washington's National Airport. The guard studied the pass that was extended by a hand from the rear window, then handed it back and spoke in an official tone. "Stay on the road. You're in a restricted area."
The driver swung onto the narrow service road that ran parallel with the east-west taxi strip on the southern border of the airport. "You sure this is the right way?" he asked, seeing nothing but an empty field.
"I'm certain," answered the gray-haired man in...