I explained to her patiently: one, I didn’t know anything about it until I got back to China. Two, the people who did know about it didn’t know the first thing about cryptography. She paced up and down the room, muttering, ‘Stupid, stupid, calling you in to help us break DIFFICULT CENTURY. They obviously don’t have a clue what they’re doing.’

I said calmly, ‘They didn’t call me in, they called you.’

‘But I’m going to need assistance, and you can’t possibly help me! This cipher is a grave dug specially for your supervisor, and if you try and help me, it’s going to be a disaster! If you’d told me this before, there’s no way I would have come with you!’

I smiled. ‘That’s why I waited until we got here before I told you. The fact is that I wasn’t really learning cryptography from Anderov. I didn’t even study maths to high-school level, so how could I even begin to?’

‘What were you doing there?’

‘Making use of my position to get information needed by cryptographers here.’

She opened her eyes wide. ‘That’s spying.’

I didn’t say anything.

She shrieked, ‘You’re a devil!’

‘And you’re an angel.’

‘You’re going to drive me to an early death.’

‘No way. I may be a devil, but I’m a devil who really appreciates you. When I’d just got back and they landed me with this, I thought the Party had made a mistake. But when I found you, I came to believe that you were the right person for the job. If they’d sent someone else, and he’d met you, he wouldn’t necessarily have given you the job, because no one else appreciates you the way I do. Perhaps that’s all thanks to Anderov. To appreciate you one needs intelligence and courage, and one needs … the experience of having lived abroad, and I have all of those …’

That evening, I couldn’t stop myself from talking a great deal to Huang Yiyi, as one intelligent person to another, as one fellow sufferer to another. I told her many of my secrets, but I think that she also understood that she was confronted with a difficult task. I hoped that the heavy burden that had been placed upon her would make her more serious, would worry her, would make her concentrate her energies on her cryptography work. But the following morning at the first meeting of the cryptanalysis group, she wasn’t there. We waited a while, and then since she didn’t turn up, in the end we just had to have the meeting without her.