The captain thought about this for a moment, then he said helplessly, ‘It’s not that I don’t want to help you, sir, the problem is … how can I put it? I can’t crack Sivincy’s code. She has written a Soviet cipher, and I have never had any contact with the Russians, let alone experience of cracking their ciphers. The whole thing would be pointless.’

‘Well, when it comes to experience with Soviet ciphers,’ Director Tie said, ‘no one has any. Relations between our countries have been so good up until now, why would we need to? The thing is that no one was expecting that Sivincy’s cipher would end up in Taiwan.’

‘Quite. Up until now they’ve always used American ciphers.’

‘So this is the first time for everyone; we’re all starting from scratch. That’s why this operation has the code-name PRIMUS. However, I’m sure all ciphers have their points of similarity, and you’ve cracked so many. There’s no one in the country with your experience and skill, and that’s why I really hope you can come and help us.’

The captain shook his head with a smile. ‘You’re wrong, sir. Ciphers simply do not have points of similarity. Russian and American ciphers are constructed on completely different principles. The former are designed to be difficult: they are complex and abstruse, and require an unusually high level of technical knowledge. The latter are designed to be tricky, and they pay a lot of attention to making them mysterious and ingenious. You could say that they are as far apart as heaven and earth. One flies into the sky, the other burrows through the earth – the difference is that great. The specialists who have created these ciphers on both sides have developed this difference intentionally, and the more pronounced the distinction is, the more successful the cipher. There’s an unwritten rule in cryptography that people who crack American ciphers don’t even try to break Russian ones, because they simply will not succeed. There are some occasions when an inch is long and a foot is short; and people are just the same: you are good at one thing and bad at another, someone else is the opposite. My situation is this: you think I’m going to be able to help you, but you’re wrong – as far as RECOVERY goes, it’s playing to all my weak points. Pretty much any mathematician you care to name is more likely to crack it than I am.’

Director Tie pointed to me and said, ‘He’s going to find us a good mathematician, but the idea of putting someone completely untried in charge of this is really nerve-racking: that’s why we came to talk to you. I thought you’d be the perfect choice; I really had no idea the whole thing would turn out to be so difficult.’