The professor held himself very stiffly, and he spoke softly, rapidly, in Chinese. “I am not involved in this, Deputy Section Chief Li. I do what I am told. No more, no less. I have no idea what is going on. But if you try to implicate me, then I can assure you, you are the one who will be in trouble.” Margaret watched his scalpel hand tremble as he spoke.

“Are you threatening me, Professor?” Li’s voice was level and steady.

“No. I am telling you how things are. And they are things over which neither of us has any control.”

“We’ll see,” Li said, and he turned abruptly and headed for the door, catching Margaret by surprise. She had no idea what had been said, but the tone was unmistakably hostile. Her brow furrowed in a question to Professor Xie that was formulated entirely in body language. After all, they had performed three autopsies together. There had been an element of bonding in that. The professor responded with an almost imperceptible shrug that carried the hint of an apology. Margaret sighed and followed Li out. She caught him up as he stepped from the cool of the building into the blaze of mid-afternoon sunshine.

“What was all that about?” she asked.

“He was warning me off.”

“What, you mean threatening you?”

“No.” Li smiled grimly. “Warning me.”

Margaret shook her head. “I don’t understand. I mean, can’t you just arrest him for obstructing a police investigation?”

“We have no such law.”

“So, what happens if someone refuses to co-operate with the police?”

Li smiled with genuine amusement at her naïveté. “No one refuses to co-operate with the police in China.”

Margaret took a moment to fully absorb his meaning. “But isn’t that what Professor Xie just did?” she asked.

Li’s smile faded. “No. He didn’t refuse to co-operate. He just lied.”

“Where is she now?” Chen stood behind his desk, eyes blazing with anger as he gathered papers together and slipped them into a briefcase.

“In my office.”

“You’re a fool, Li,” Chen raged. “I told you she was to play no further part in this investigation.”

“She’s a witness. I’m taking her statement.”

“Proving what? That Professor Xie’s English is less than perfect? For God’s sake, Li, what possible reason could the professor have for deliberately destroying evidence or failing to carry out blood tests?”

“None.”

“Well, there you are, then.”

“He was ordered to.”

Chen’s laugh was hollow and without humour. “Oh, what’s this? A conspiracy theory now? Dr. Campbell is turning out to be the biggest mistake I ever made.” He rounded the desk and unhooked his jacket from a peg on the back of the door.

“It’s got nothing to do with Dr. Campbell.”