Like most women – and here Fiona evidenced women customs and immigration officers, women police officers and secretaries in her own office – she was more conscientious and painstaking than her male peers. Her detached contempt for Bret, and other men like him, was best demonstrated by doing her job with more care and skill than he did his. She would become this damned 'superspy' they wanted her to be. She would show them how well it could be done.

Fiona's meetings with Martin Euan Pryce-Hughes continued as before, except that Bret made sure that the little titbits she was able to throw to him, and the responses to his requests for specific information, were better than the Spielmaterial he'd been given before. Pryce-Hughes was pleased. Reacting to a broad hint from him Fiona asked for more money: not much more but enough to assert her worth. Moscow responded promptly and generously and this pleased Bret, and pleased Pryce-Hughes too. And yet, as month after month became a year, and time went on and on, she began to hope that the Department's long-term plan to place her in the enemy camp would be abandoned. Bret continued with their regular briefing sessions, and her duties were arranged to that purpose. Her use of the computers was strictly denned and she never handled very sensitive papers. But the D-G appeared to have forgotten about her, and forgotten about Bret Rensselaer too. Once or twice she came near to asking the D-G outright, but decided to let things continue. Bernard said the D-G was becoming eccentric to the point of disability but Bernard always inclined to overstatement.

Typically it was her younger sister, Tessa, who made the whole thing erupt again. 'Darling, Fi! You are always there when I need you.'

'You have such good champagne,' said Fiona, in an effort to reduce the tension that was evident in her sister's face, and in the way she constantly twisted the rings on her fingers.

'It's my diet: caviar, champagne and oysters. You can't get fat on it.'

'No. Only poor,' said Fiona.

'That's more or less what Daddy said. He disapproves.' As if in contravention Tessa picked up her glass, looked at the bubbles and then drank some champagne.

Tessa had always shown a constitutional spirit that bent towards trouble. The relationship between Fiona and her younger sister provided a typical example of sibling rivalry – it was a psychological phenomenon to which Bret referred many times during their sessions together. Their father, a single-minded man, had his favourite motto ('What I want are results not excuses') embroidered on a cushion displayed on the visitor's chair in his office. He believed that any form of forgiveness was likely to undermine his daughters' strength and his own.

Tessa had discovered how undemanding and convenient it was to play the established role of younger child, and let Fiona fulfil, or sometimes fail to fulfil, her father's expectations. Tessa was always the one of whom little was expected. Fiona went to Oxford and read Modern Greats; Tessa stayed at home and read Harold Robbins. Temperamental, imaginative and affectionate, Tessa could turn anything into a joke: it was her way of avoiding matters that were demanding. Her own boundless generosity made her vulnerable to a world in which people were so cold, loveless and judgemental. In such a world did it matter too much if she indulged in so many frivolous little love affairs? She always went back to her husband and gave him her prodigious love. And what if, one casual night in bed with this silly drunken lover, he should confide to her that he was spying for the Russians? It was probably only a joke.

'Describe him again,' said Fiona.

'You know him,' said Tessa. 'At least he knows all about you.'

'Miles Brent?'

'Giles Trent, darling. Giles Trent.'

'If you'd stop eating those damned nuts I might be able to understand what you are saying,' she said irritably. 'Yes, Giles Trent. Of course I remember him.'

'Handsome brute: tall, handsome, grey wavy hair.'

'But he's as old as Methuselah, Tessa. I always thought he was queer.'

'Oh, no. Not queer,' said Tessa and giggled. She'd had a lot of champagne.

Fiona sighed. She was sitting in Tessa Kosinski's elaborately furnished apartment in Hampstead, London's leafy northwestern suburb, watching the blood-red sun drip gore into the ruddy clouds. When, long ago, London's wealthy merchants and minor aristocracy went to take the waters at regal and fashionable Bath, the less wealthy sipped their spa water in this hilly region that was now the habitat of successful advertising men and rich publishers.

Tessa's husband was in property and motor cars and a diversity of other precarious enterprises. But George Kosinski had an unfailing talent for commercial success. When George bought an ailing company it immediately recovered its strength. Should he wager a little money on unwanted stock his investment flourished. Even when he obliged a local antique dealer by taking off his hands a painting that no one else wanted, the picture – dull, dark and allegorical – was spotted by one of George's guests as the work of a pupil of Ingres. Although many nonentities can be so described, Ingres' pupils included the men who taught Seurat and Degas. This, the coarse canvas and the use of white paint so typical of the Ingres technique, was what persuaded the trustees of an American museum to offer George a remarkable price for it. He shipped it the next day. George loved to do business.

'And you told Daddy all this: Trent saying he was a Russian spy and soon?'

'Daddy said I was just to forget it.' Idly Tessa picked up a glossy magazine from the table in front of her. It fell open at a pageful of wide-eyed people cavorting at some social function of the sort that the Kosinskis frequently attended.

'Daddy can be very stupid at times,' said Fiona with unmistakable contempt. Tessa looked at her with great respect. Fiona really meant it: while Tessa – who also called her father stupid, and worse, from time to time – had never completely shed the bonds of childhood.

'Perhaps Giles was just making a joke,' said Tessa, who now felt guilty at the concern her elder sister was showing.

'You said it wasn't a joke,' snapped Fiona.

'Yes,' said Tessa.

'Yes or no?'

Tessa looked at her, surprised by the emotions she had stirred up. 'It wasn't a joke. I told you: I went all through it with him… about the Russian and so on.'

'Exactly,' said Fiona. 'How could it have been a joke?'

'What will happen to him?' Tessa tossed the magazine on to a pile of other such periodicals.

'I can't say.' Fiona's mind processed and reprocessed the complications this would bring into her life. She looked at her younger sister, sitting there on the – yellow silk sofa, in an emerald-green Givenchy sheath dress that Fiona – although the same size – could never have got away with, and wondered whether to tell her that she might be in physical danger. If Trent told his Soviet contact about this perilous indiscretion it was possible that Moscow would have her killed. She opened her mouth as she tried to think of some way to put it but, when Tessa looked at her expectantly, only said, 'It's a gorgeous dress.'

Tessa smiled. 'You were always so different to me, Fi/

'Not very different.'

'The Chanel type.'

'Whatever does that mean?'

Teasingly Tessa said, 'Tailleur, with a jacket lined to match the blouse, chain belt and gardenia; everyone knows what a Chanel type looks like.'

'What else?' Sometimes Tessa's manner could be trying.

'I knew you would end up doing something important… something in a man's world,' said Tessa very quietly as she waited for her sister to pronounce on what might happen next. When Fiona made no reply, Tessa added, 'I didn't ask Giles what he did: he just came out with it.'