'Hi, can I buy you a drink?'

I turned to find a man, a thin tall guy, in faded denim jeans and a tie-dyed T-shirt, with long dark hair and a moustache. He had pale blue eyes and – as far as I could tell in the state I was currently occupying, poised on my ridge, wondering which way to go – he looked pretty damned nice. I held up my vodka and tonic to show him.

'I'm fine, thanks.'

'Have another. They close in ten minutes.'

'I'm with a friend, over there,' I said, pointing with the glass at Hamid.

'Shame,' he said, and wandered off.

My hair was down and I was wearing new straight-legged jeans and a puff-sleeved ultramarine V-neck T-shirt that showed three inches of cleavage. I had my high boots on and I felt tall and sexy. I would have fancied me, myself… I let the illusion warm me for a while before adding the pointed reminder that my five-year-old son was staying with his grandmother and I didn't want to be hungover when I went to pick him up. This would be my last drink, definitely.

Hamid came over to the bar and joined me. He was wearing his new leather jacket and a cornflower-blue shirt. I put my arm round his shoulders.

'Hamid!' I exclaimed in feigned dismay. 'I can't believe you're leaving. What're we going to do without you?'

'I can't believe it neither.'

'Either.'

'Either. I'm very sad, you know. I was hoping that-'

'What were they teasing you about?'

'Oh – Indonesian girls, you know. Very predictable.'

'Very predictable. Very predictable men.'

'Would you like another drink, Ruth?'

'I'll have another vod and ton, thanks.'

We sat on bar stools and waited for our drinks to be served. Hamid had ordered a bitter lemon – and it struck me suddenly that he didn't drink alcohol, of course, being a Muslim.

'I'll miss you, Ruth,' he said. 'Our lessons – I can't believe I'm not coming to your flat on Monday. It's over three months, you know: two hours a day, five days a week. I counted: it's over 300 hours we've spent together.'

'Bloody hell,' I said with some sincerity. Then I thought, and said, 'But you've had three other tutors as well, remember. You spent as much time with Oliver…' I pointed, 'and Pauline, and Whatsisname, over by the juke-box.'

'Sure, yeah,' Hamid said, looking a little hurt. 'But it wasn't the same with them, Ruth. I think it was different with you.' He took my hand. 'Ruth-'

'I have to go to the loo. Back in a tick.'

The last vodka had tipped me off my ridge and I was sliding, tumbling down the other side of the mountain in a skidding flurry of schist and scree. I was still lucid, still functioning, but my world was one where angles were awry, where the verticals and horizontals were no longer so fixed and true. And, curiously, my feet seemed to be moving faster than they needed. I barged brusquely through the door into the passageway that led to the toilets. There was a public phone here and a cigarette machine. I suddenly remembered I was almost out of cigarettes and paused by the machine but, fumbling, rummaging for change, I realised that my bladder was making more importunate demands on my body than my craving for nicotine.

I went into the loo and had a long, powerfully relieving pee. I washed my hands and stood in front of the mirror. I looked at myself square in the eye for a few seconds and pushed my hair around a bit.

'You're pissed, you silly bitch,' I said out loud, though softly, through my teeth. 'Go home.'

I walked back into the passageway and Hamid was there, pretending to be making a phone call. From the pub the music surged louder – 'I heard it on the grapevine' – almost a Pavlovian sexual trigger for me and somehow, in some manner, in some brief gap in the space/time continuum, I found myself in Hamid's arms and was kissing him.

His beard was soft against my face – not raspy and jaggy – and I stuck my tongue deep in his mouth. I suddenly wanted sex – it had been so long – and Hamid seemed the perfect man. My arms were around him, holding him tight to me, and his body felt absurdly strong and solid, as if I was embracing a man made from concrete. And I thought: yes, Ruth, this is the man for you, you fool, you idiot – good, decent, kind, a friend to Jochen – I want this engineer with his soft brown eyes, this solid, strong man.

We broke apart and, as it inevitably does, the dream, the wish, seemed immediately less potent and desirable, and my world steadied slightly.

'Ruth -' he began.

'No. Say nothing.'

'Ruth, I love you. I want to be your husband. I want you for my wife. I'll come back in six months from my first tour. I have a very good job, a very good salary.'

'Don't say anything more, Hamid. Let's finish our drinks.'

We went back into the bar together – last orders were being called but now I didn't want any more vodka. I searched in my handbag for my last cigarette, found it and managed to light it reasonably competently. Hamid was distracted by some of his Iranian friends and they had a quick exchange in Farsi. I looked at them – these handsome, dark men with their beards and moustaches – and watched them shake hands in a strange way – high, gripping thumbs, then smoothly altering the grip again, as if they were exchanging some covert signal, acknowledging some membership of a special club, a secret society. And it was this thought that must have made me recall Frobisher's invitation and, for some stupid, over-confident, drunken reason, it suddenly seemed worth pursuing.

'Hamid,' I said, as he sat down beside me again, 'do you think there might be SAVAK agents in Oxford?'

'What? What are you saying?'

'I mean: do you think some of these engineers have been planted here, pretending to be students but all the while working for SAVAK?'

His face changed; it became very solemn.

'Ruth, please, we must not talk of such things.'

'But if you suspected someone, you could tell me. It would be a secret.'

I misread the expression on his face – that can be the only explanation for what I said next. I thought I had stirred something in him.

'Because you can tell me, Hamid,' I said, softly, leaning closer. 'I'm going to be working with the police, you see, they want me to help them. You can tell me.'

'Tell you what?'

'Are you with SAVAK?'

He closed his eyes and, keeping them closed, said: 'My brother was killed by SAVAK.'

I tried to vomit by the wheelie bins at the back of the pub, but failed, managing only to hawk and spit. You always think you'll feel better if you vomit but actually you feel much worse – and yet still you try to empty your stomach. I walked with due care to my car and methodically checked it was locked and that I hadn't left anything temptingly thievable on any seat and then set off on the long walk home back to Summertown. Friday night in Oxford – I'd never find a taxi. I should just walk home and, perhaps, it might sober me up. And tomorrow Hamid was flying off to Indonesia.

London . 1942

EVA DELECTORSKAYA WATCHED ALFIE Blytheswood leave the side entrance of Electra House and duck into a small pub off the Victoria Embankment called the Cooper's Arms. She gave him five minutes and then went in herself. Blytheswood stood with a couple of friends at the bar of the snug, drinking a pint of beer. Eva was wearing spectacles and a beret and she approached the bar herself and ordered a dry sherry. If Blytheswood glanced up from his conversation he would easily spot her, though she was confident he wouldn't recognise her, the new length and colour of her hair seeming to alter her appearance significantly. However, she had put on the spectacles at the last moment, suddenly a little unsure. But she had to test her disguise, her new persona. She took her sherry to a table by the door, where she read her newspaper. When Blytheswood left, walking past her table, he didn't even glance at her. She followed him to his bus stop and waited with the others in the queue for his bus to arrive. Blytheswood had a long journey ahead of him, north to Barnet, where he lived with his wife and three children. Eva knew all this because she had been shadowing him for three days. At Hampstead a seat behind him was vacated and Eva slipped quietly into it.