“I was too young,” she said, shaking her head. “But Katerina was older and they had other plans for her. Her instructor handed her a knife one day and told her to kill him. Katerina obeyed. Katerina always obeyed.”

“Go on.”

“Even after he disarmed her, she kept coming at him. Eventually, she cut herself on her own weapon. She’s lucky she didn’t bleed to death.” Madeline looked down at the photograph. “Where do you think she is now?”

“I suppose she’s somewhere in Russia.”

“In a town without a name.” Madeline returned the photograph to Gabriel. “Let’s hope she stays there.”

When Gabriel returned to Wormwood Cottage, he climbed the stairs to his room and fell exhausted into his bed. He longed to telephone his wife but didn’t dare. Surely, his enemies were prowling the grid for traces of his voice. Dead men didn’t make phone calls.

When sleep finally claimed him, he was made restless by dreams. In one he was crossing the nave of a cathedral in Vienna, carrying a wooden case filled with his restoration supplies. A German girl waited in the doorway to engage him in conversation, as she had done that night, but in his dream she was Katerina and blood flowed freely from a deep wound to her arm. “Can you repair it?” she asked, showing him the wound, but he slipped past her without a word and made his way through quiet Viennese streets, to a square in the old Jewish Quarter. The square was blanketed with snow and jammed with London buses. A woman was trying to start the engine of a Mercedes sedan but the engine wouldn’t turn over because the bomb was pulling power from the battery. His son was strapped into his car seat in the back, but the woman behind the wheel was not his wife. It was Madeline Hart. “How did you find me?” she asked through the broken glass of her window. And then the bomb exploded.

He must have called out in his sleep because Keller was standing in the doorway of his room when he woke. Miss Coventry served them breakfast in the kitchen and then saw them into the cold foggy morning as they set off for a hike across the moor. Gabriel’s legs were weak with inactivity, but Keller took mercy on him. They passed the first mile at a moderate pace that increased gradually as Gabriel spoke of Madeline and the offspring of a KGB honey trap named Katerina. They were going to find her, said Gabriel. And then they were going to send a message to the Kremlin that needed no translation.

“Don’t forget Quinn,” said Keller.

“Maybe there was no Quinn. Maybe Quinn was just a name and a track record. Maybe he was just a piece of bait they tossed into the water to lure us to the surface.”

“You don’t really believe that, do you?”