“Ah.” Mei Yuan held out a plump hand. “Are you here on holiday or on business?”

Margaret was taken aback by the perfect English that rolled fluently off the tongue of what she had taken to be a peasant street vendor. “I’m lecturing at the People’s University of Public Security,” she said.

“And are you a practising pathologist, or an academic?”

Again Margaret was startled. “Practising,” she said. “I only lecture part-time.” And then, “You speak excellent English.”

“Thank you,” Mei Yuan said. “I get very little chance to practise it nowadays. So I am what you would call a little rusty.”

“No, not at all.” Margaret glanced at Li for illumination.

“Mei Yuan was a graduate of art and literature at Beijing University in the late fifties,” he said.

Mei Yuan added, without any apparent regret, “But my life did not follow an academic course. I spent most of it in the countryside in Hunan province. I only returned to Beijing a few years ago when my husband died.” She turned to Li. “You missed breakfast.”

“I was too early for you.”

“I think, perhaps, my riddle was too difficult for you. You were avoiding me.”

Li laughed. “No, I wasn’t. I figured that out yesterday afternoon.”

“Figured what out?” Margaret asked.

Li shook his head, smiling. “It’s a sort of game we play,” he explained. “I usually stop for breakfast on the way to work. Mei Yuan will pose me a problem, or a riddle. I’ve got till the next day to figure it out. If I come up with the right answer, I set her one. Mind games.”

Mei Yuan laughed. “Mindless games. For people with nothing better to do at that time of the morning.”

“So what was the riddle?” Margaret was intrigued.

“There are two men,” said Li. “One of them is the keeper of all books, giving him access to all knowledge. Knowledge is power, so he is very powerful. The other has only two sticks. But they give him more power than the other. Why?”

Margaret thought for a moment. “That’s easy,” she said.

Li looked at her sceptically. “Oh, sure.”

“We have a saying at home about not having two pennies to rub together—meaning you are very poor. But if you have two sticks to rub together, you can make fire. And if you can make fire you can burn books and destroy the knowledge they contain. You take away knowledge, you take away power.”

Mei Yuan clapped her hands in delight. “Very good.”

Li was astonished, and full of grudging admiration. “It took me all day to work that out.”

Margaret grinned, and as Mei Yuan prepared their jian bings asked her about the book she was reading.

“Meditations,” she said.

“Descartes?” Margaret was taken aback.

Mei Yuan nodded. “Have you read it?”

“No. I suppose I should have. But there are so many books. You can’t read them all.”