‘Exactly,’ she said. ‘We can be sure that RECOVERY is an algorithmic cipher, so now what I want to ask you is: given your knowledge of Sivincy, when she was designing RECOVERY twenty years later, what kind of encryption method would she use? I don’t want you to think about it, just tell me straight out.’

‘Number one: a super-large-value algorithmic cipher encrypted with a medium-large-value algorithmic cipher. If you give me a second choice, I would say …’

She cut me short. ‘You don’t get a second choice.’

‘So which would you pick?’

She sighed deeply. ‘To be quite frank, I have no feel for this, and it’s giving me a headache. Up until now I’ve always had a kind of sixth sense for this sort of thing, but this time it’s simply not working.’

‘Maybe Sivincy’s tiresome traps are affecting your feel for it.’

‘Do you think she has more nasty surprises in store for us?’

‘Well, as I just said, if I were given a second guess …’

She said shortly, ‘You don’t have a second choice; your second guess is pointless.’ After a short pause she added, ‘I really wish that I was talking to Anderov himself rather than one of his students. If Anderov made the same choice I could eliminate it straight away. Why do you think Anderov hasn’t replied to your letter?’

‘No idea,’ I said.

After that she demanded that we go for a walk. On the way home she insisted on inviting me in. I said no, it was already late and I wanted to go to bed. She said that it was still early, just past nine o’clock, so let’s go. That whole evening we had done nothing but talk about ciphers, so I didn’t want to annoy her. I actually thought that she wanted to carry on talking about ciphers, so even though I was uncomfortable about the whole thing, in the end I went with her.

It was the first time I had ever been to her room, and she had arranged it very nicely, and very distinctively. On the wall above her bed she had stuck a poster of the American film star Marilyn Monroe which really caught my attention: she was bending down so that her hands were on her knees, but her head was raised to look out at you, her generous lips slightly parted, her whole body expressing longing!

I couldn’t help wondering what kind of person admired that sort of film star.