THE SUDDENNESS with which they reached the center of Washington took Gabriel by surprise. One moment they were on a two-lane rural road at the edge of the Potomac gorge, the next they were crawling along Q Street through the Georgetown evening rush. Carter, playing the role of tour guide, pointed out the homes of the neighborhood’s most celebrated residents. Gabriel, head against the window, couldn’t summon the energy even to feign interest. They crossed a short bridge, guarded at each end by a pair of enormous tarnished buffalos, and entered the city’s diplomatic quarter. Just beyond Massachusetts Avenue, Carter pointed to a turreted redbrick structure on the left side of the street. “That’s the Phillips,” he said helpfully. Gabriel looked to his right and saw a bronze version of Mohandas Gandhi hiking across a tiny triangular park. Why Gandhi? he wondered. What did the ideals of the Mahatma have to do with this patch of American global power?

Carter drove another block and parked in a restricted diplomatic zone outside a tired-looking Latin American embassy. He left the engine running and made no movement to indicate he intended to get out of the car. “This part of town is called Dupont Circle,” he said, still in tour guide mode. “It’s what passes for avant-garde in Washington.”

An officer of the Secret Service Uniformed Division rapped his knuckle on Carter’s window and gestured for him to move along. Carter, eyes straight ahead, held his ID against the glass, and the officer walked back to his squad car. A moment later something caught Carter’s attention in the rearview mirror. “Here she comes,” he said.

Gabriel looked out his window as Sarah Bancroft floated virtuously past, dressed in a long dark overcoat with a narrow waist. She held a leather briefcase in one hand and a cell phone in the other. Gabriel heard her voice briefly as she passed. Low, sophisticated, a trace of an English accent—a remnant, no doubt, of her time at the Courtauld and a childhood spent in international schools abroad.

“What do you think?” asked Carter.

“I’ll let you know in a minute.”

She came to the corner of Q Street and 20th Street. On the opposite corner was an esplanade filled with sidewalk vendors and a pair of escalators leading to the Dupont Circle Metro station. The traffic light in Sarah’s direction was red. Without stopping she stepped from the curb and started across. When a taxi driver sounded his car horn in protest, she shot him a look that could melt ice and carried on with her conversation. Then she continued slowly across the intersection and stepped onto the down escalator. Gabriel watched with admiration as she sank slowly from view.

“Do you have two more just like her?”