“You’re right. It hasn’t. This is an investigation by Section One of the Criminal Investigation Department of Beijing Municipal Police.” He pulled his jacket on angrily.

“The point is, someone tried to stop us doing tests on Chao’s blood, Chief.”

“Well, if that’s true, they succeeded, didn’t they?” He looked at his watch. “Look, I’ve got a meeting at the Procurator General’s office. I’m going to be late.” He paused at the door and cast Li a withering look. “Perhaps you’d like me to pass on your conspiracy theory to Deputy Procurator General Zeng, since you and he seem very tight on this case.”

Li followed him out into the corridor, ignoring the barb. “Chief, I think the key to this whole case is in what those blood tests would have shown up.”

“Then find another key. There’s always a back door.” Chen checked his watch again without breaking his stride. “And, for heaven’s sake, lose the American. I hear she’s quit her job at the university.”

“She’s booked a flight home tomorrow morning.”

“Good. Make sure she’s on it.”

Li stopped and watched Chen all the way to the end of the corridor, then turned into the detectives’ room, ignoring the curious glances of his colleagues and passing straight through into his own office. He slammed the door behind him. Margaret was sitting at his desk, tipping the chair slowly backwards and forwards.

“It’s strange to think he was in here,” she said. She lifted a copy of Johnny Ren’s photograph from the desk. “I take it this is him?” Li nodded. “He doesn’t look at all like I imagined him.”

“How did you think he’d look?”

“Not Chinese. I don’t know why. I knew he would have to be, but it’s not the picture I had in my head.” She examined the photograph again. “He’s got evil eyes, hasn’t he? There’s no light in them. They’re quite dead.” She looked up. “What did Chen say?”

“He’s not buying into a conspiracy.”

“Are you surprised?”

“Not really. He thinks Professor Xie’s story sounds quite plausible.”

“So where does that leave us?”

“It leaves me trying to catch Johnny Ren. And it leaves you catching a plane home in the morning.” He glanced at her, then quickly averted his eyes, suddenly self-conscious. He wandered to the window, hands pushed in pockets, and there was a silence between them that lingered interminably.

Finally she said, “Of course, there could be another way of getting access to Chao’s medical history.”

He turned, frowning. “How do you mean?”

“Well, presumably he had a doctor. I mean, where else would he get all those prescription drugs?”

Li shook his head in disbelief. It was so obvious, why had it taken both of them until now to think of it? And then he smiled to himself.