“But this is China, not the United States.”

“You told me no one in China refused to co-operate with the police.”

“Of course, I will ask for the records,” he said.

“And if they won’t give you them?”

“They’ll have to have a very good reason.” His words sounded braver than he felt. He felt like a weak swimmer who has strayed further from shore than he intended and is a long way out of his depth.

“Okay,” Margaret said. “Let’s think about this. We’re dealing here with someone who has a great deal of power and influence. Someone with enough clout to have Chao admitted to a high-security hospital. Perhaps the same person who hired Johnny Ren to murder him and is now trying to stop you from finding out why. But this is not some all-powerful, or even infallible, individual. He’s made mistakes. Like making a mess of getting rid of the evidence, if that’s what Chao was. He clearly thought that burning the body would destroy whatever it was in his blood they wanted to hide. It didn’t. Then they made a real clumsy job of stopping us doing the AIDS test. Incinerating the body, for Christ’s sake, and all the samples! An administrative error? That’s not going to hold up for five minutes if you pursue it hard enough.”

“But he didn’t have AIDS. We know that. So why were they trying to stop us from testing for it?”

“In case we found something else. Something they didn’t want us to find.”

“What?”

Margaret shook her head in frustration. “I don’t know.”

“And what about the other two murders? DNA tests prove that all three were killed by Ren. What’s the connection?” Li felt the beginnings of a headache. The deeper they got into this, the muddier the waters were becoming.

“I don’t know,” Margaret said again. She was beginning to realise how little they really knew about any of it. “All I know is that someone must have been watching your investigation every step of the way. Someone with detailed access to your every move, and an understanding of the implications of everything you’ve done.”

Li frowned. “What makes you think that?”

“How else would Johnny Ren have known who was leading the case? How would he have known who to follow? How else would anyone know the autopsy results, or that you had asked for an AIDS test? I mean, who else knew about any of it outside the department?”

“No one,” Li said aggressively. He couldn’t believe she was suggesting that someone in Section One was implicated. Then he was struck by a thought that turned his blood to ice. “Except . . .” He didn’t even dare to voice the thought.

“Except who?” When he didn’t respond, Margaret asked again, “Except who, Li Yan?”

“Deputy Procurator General Zeng.”

Her brows furrowed in consternation. “Who?”