‘I’ve heard of you, Chief Inspector Chen. You may not be a bad cop. And according to my late wife, who read your poems, you may not be a bad writer, either. Still, you don’t have to waste your time with me. I’m innocent, as I’ve told Detective Yu. I won’t say anything else. It’s far more important for you to concentrate on the investigation against the environmental activist.’

‘Coincidentally, the activist named Shanshan is making a documentary about the disastrous air pollution in China. It is truly an important, meaningful project – whatever investigation my boss in Beijing may want me to do – and I pledge myself to keep any harm from happening to her. On the contrary, I will ensure the eventual release of her documentary.’

It was the first time Yu had learned anything about Chen’s investigation under Zhao. The way Chen spoke about it reminded Yu of something Peiqin had told him, the romantic experience of the poet inspector in Wuxi, but it was not a moment for his thoughts to wander away from the present case, Detective Yu hastened to tell himself.

‘You really mean that, Chief Inspector Chen?’ Lou said, looking up with a sudden light in his eyes, as if Chen had been sitting opposite him across the desk.

‘Yes, I give you my word, Lou.’

‘Chief Inspector Chen keeps his word,’ Yu cut in. ‘I’ve been his partner for years, I know.’

‘Now Detective Yu wants me to make this conference call about the yellow mask serial murder—’

‘Yellow mask serial murder?’

‘The yellow masks come from the Shanghai Number One People’s Hospital, in which your wife passed away, I know, and I’m sincerely sorry about it. So many people get terribly sick because of the contaminated air, and the hospital provides the specially treated masks to the in-house patients against cross-infection, and to their visiting family members and the hospital staff members, too.’

There was no immediate response from Lou. Yu thought he detected a nervous twitching at the corner of the man’s mouth.

‘It’s not too far-fetched to see the connection between the illness and the air pollution, I understand. Much more should have been done about the environmental crisis, like the documentary I’ve mentioned, to call people’s attention to the disaster. Of course, there are ways of striving for that purpose. In your case, you planted the yellow masks at the crime scenes – in a symbolic protest against the catastrophic pollution. In memory of her, but also much more than that. As a wake-up call to reach as many people as possible, what could have worked out more effectively than a sensational serial murder?’

Lou still made no response, but he breathed more heavily. Yu pushed a cup of water across the table to him.

‘In that way, you’re trying to immortalize her memory in a unique way—’

‘Don’t say any more!’

‘But I don’t think the government will ever let the message of the yellow mask serial murder be known.’