Once, at his school, it had boiled over. A bully, the biggest boy in his year, was mercilessly baiting one of the juniors, a soft boy with a deformed hand of which he was crushingly self-conscious. He was almost hysterical with shame and embarrassment at the bully’s cruelty. A crowd had gathered, the way that crowds do, scared, fascinated, glad that it wasn’t them. Li broke through the circle of boys and told the bully to stop. The boy was not used to being challenged. He turned, wild-eyed, and demanded to know who the hell Li thought he was. Li said, “I am Li Yan. And if you do not stop I will break your skull.” And he meant it. And the bully saw in his eyes that he meant it. But he was trapped by his own weakness. He could not back down without losing face. So Li had to crack his skull. He was in hospital for nearly two weeks and Li was visited by the juvenile delinquency officer and almost expelled from his school. But no one ever bullied the boy with the deformity again, not while Li was around. And Li had never had to fight anyone else again since.

So he knew that this girl was wrong. He was not made for better things. He was made to be a policeman, and to Li that was the very best thing he could be. He had never regretted coming to Beijing, and the last he heard the girl he walked by the canal with had married the bully whose skull he’d cracked. He had smiled, for the bully was weak, and she was strong and would mould him into whatever she wanted.

Margaret, he noticed now, was scribbling in a notebook whatever was being relayed to her across the ether. She nodded and smiled and hung up the phone, tearing the page out of the notebook before coming through. She handed it to Li, a gleam in her eyes. “Chao Heng,” she said. “That’s the name of your John Doe through there.” She jerked her thumb towards the autopsy room. “About ninety-nine per cent certain.”

Li looked at the piece of paper. She had scribbled, Chao Heng, graduated microbial genetics, University of Wisconsin, 1972.

He looked up at her in astonishment. Professor Xie said, “How can you possibly know this?”