Seraut ignored my question and continued walking down the corridor. I lingered behind, looking carefully through the window and trying to take a mental photograph of the room. It was like seeing evidence of a crime that was unfolding in real time, with me and Bowman the only witnesses. I felt as if I had been interposed in history, given a chance to stop something terrible from happening. Imagine that you had visited the Wannsee Conference in Nazi Germany as the Holocaust was being planned. What would you have done? How could you have stopped the machine of inevitability? Simply to witness—to report—would not have been enough. You had to act.

“Is Mr. Navarre here?” I asked. Our host continued to ignore me. Arthur picked up the cue.

“Yes, what about Roger Navarre?” he pressed. “You mentioned earlier he was in his lab. We’d like to just say hello to him, briefly, if we could. I would hate to tell Michel Bézy that we came all the way out here without at least shaking hands with him.” I was awed by Bowman’s performance. With those few words he had backed Seraut gently into a corner. Each time Arthur invoked Bézy the same look of anxious deference came over the Frenchman’s face.

“I will see if Roger can be interrupted,” he said. He walked to the end of the corridor, where he unlocked a large metal door.

I turned to Bowman. “I need to talk to Navarre alone, for thirty seconds, if you can find any way to distract our host.” Arthur nodded; he understood.

The door of the laboratory swung open, and a small man with a shock of black hair emerged. He walked slowly toward us, accompanied by Seraut. He was the same man I had met before, but his complexion was much more sallow, and there were deep circles under his eyes. It was the haggard look of a prisoner.

“How do you do?” said Navarre, shaking our hands. “I am pleased to meet you. I do not have many visitors here.” He studied my face. A flicker of recognition came into his eyes, but he said nothing.

Bowman took Seraut aside. “Let me explain about Bézy,” he said in a confidential voice. “He pays me a great deal of money. I can explain it to you, entre nous.” Bowman steered our host a few yards down the hall for a private conversation, giving me an opportunity to talk in confidence with Navarre.

“I know you,” whispered the Frenchman. His eyes were dancing now. “You came to my laboratory in Paris.” There was a look of wonder on his face. Someone from his old life had come to see him.

“Yes. I have to ask you some questions, Mr. Navarre. How is your research going here? Do you have any concerns about it?”

“The research is very bad. He lowered his voice. “I am not happy here.”