he flight to Madrid was half-empty. Without having to be asked, Kit left Fiona with a double seat to herself and moved across the aisle, where he flipped up the screen of his laptop and started work as soon as they were in the air, his Walkman rendering him oblivious to any outside distractions. On the way to the airport, he'd nagged her about making a start on the thick bundle Steve had had delivered to the house, which Fiona had been studiously ignoring for the past two days. She'd been hiding behind the necessity of familiarizing herself with the material from Toledo, but if she was honest, she'd been as thorough with that as she could be. Now she had no excuse, and the flight was just long enough to get a flavour of what she had to digest.

The first section began with a page of personal ads from Time Out. During the course of his lengthy police interviews, Blake had admitted that although he had a long-term relationship with an air hostess, he also replied to women who advertised in the lonely hearts column. He'd said that he went for the ones who seemed insecure, because they were always grateful to meet a good-looking bloke like him. He'd admitted he was interested principally in sex, but insisted that he didn't want to waste his time on brainless bimbos. From what Fiona remembered of the original interview transcripts, Blake had seemed confident, even arrogant about his capacity to attract women; a man who knew what he wanted and didn't doubt he could get it. He certainly hadn't come over as weak or inadequate.

Based on his interpretation of the interviews, Horsforth had constructed several ads that he felt would appeal to their suspect. The first attempts had produced plenty of responses, though none was from Blake. "So much for getting inside the head of the killer," Fiona muttered under her breath. But the second round snared their target. He had responded to: "SWF, 26, slim, new to N. London, seeks male guide for conversation,

meals, movies and an introduction to the bright lights and good times. GSOH. Pictures please."

Blake had described himself as a professional man of twenty-nine with an interest in cinema, reading, walking in London's parks, and enjoying female company. Under Andrew Horsforth's guidance, Detective Constable Erin Richards had written the reply.

"Dear Francis," it read. "Thanks for your letter, it was easily the most charming of all the ones I've received. I must confess I'm a little nervous about this because it's not the sort of thing I normally do. Would it be OK with you if we exchanged a couple more letters before we actually meet?

"Like you, I'm interested in going to the cinema. What kind of films do you like best? Although I know it's probably not what women are supposed to enjoy, I love all those wonderful dark thrillers like Seven, Eight Millimetre and Fargo, and Hitchcock films like Psycho. But they've got to have a good plot to keep me going. As for reading, I don't get to read as much as I should. I like Patricia Cornwell, Kit Martin and Thomas Harris best, and I sometimes read true crime too.

"I don't really know London well enough to know where it's safe to go walking. You read about such terrible things sometimes in the papers, people being mugged and raped in parks, that it makes me a bit nervous because I'm a stranger. Perhaps you could show me some of your favourite walks sometime?

"I work in the civil service. Nothing very exciting, I'm afraid. I'm a clerk at the Ministry of Agriculture. I moved here from Beccles in Suffolk after my mother died. There was nothing to keep me there, because my father passed away a couple of years before her, and I've no brothers or sisters, so I thought I'd come looking for adventure in London!

"I'd love to hear from you again if you think we might have enough in common to enjoy each other's company. You can write to the box office number because I'm keeping it on for a couple of weeks longer. "Yours sincerely, "Eileen Rogers."

Blake had replied by return of post. "Dear Eileen," he'd written. "Thanks for your lovely letter. Yes, it does sound as if we'd have a lot in common. We seem to go for the same kind of books and films for a start.

"I can understand why you might feel a bit nervous walking around London on your own. I've lived here all my life but there are many parts of the city I don't know at all, and if I have to go there for work I sometimes feel a little anxious because it's so easy to end up somewhere that can feel threatening just because it's unfamiliar. It must be so much harder for a woman on her own. I'd be happy to show you around. I know Hampstead Heath and Regent's Park and Hyde Park well, I go there often.

"I realize you must be a bit nervous about meeting a stranger like me, but I'd like to talk face to face. I can't help thinking we would have a lot to say to each other. We could meet somewhere public, like they recommend you should for a first time. I could meet you on Saturday afternoon and we could have coffee together. I thought we could meet outside the Hard Rock Cafe at Hyde Park Corner at three o'clock. You can phone me to confirm the arrangements if you like.

"Please say yes. You sound just the kind of woman I want to meet. "Best wishes, "Francis Blake."

The fish had swallowed the bait remarkably easily, Fiona thought. It wasn't so much that Horsforth had been particularly clever or subtle in the way he'd orchestrated the approach, as that Blake had been surprisingly eager to make the contact, in spite of having been the subject of such close police attention. Perhaps that was why he'd been so keen; he was desperately in need of a respite with someone who knew nothing of what he'd been through at the hands of the law. For a man who apparently liked to be in control, it must have been infuriating to be surrounded by people who thought they knew more about him than they really did. A stranger who knew nothing of his role as a suspect would allow him to feel relaxed.

Whatever the reasons, it had provided the opportunity for the operation to go ahead. DC Richards had phoned Blake and arranged to meet. The call had lasted for about ten minutes, Fiona noted. They'd chatted without much awkwardness, mostly about films they'd seen recently, then made arrangements to meet. At their first encounter, as on every subsequent one, Richards was wired for sound, transmitting the conversation to a back-up radio van that kept discreet tabs on the pair of them throughout.

Richards had played her role well, striking an appropriate balance between edgy nervousness and eager friendliness. They'd gone for coffee, then Blake had suggested a short walk through the park before they parted. As they'd walked, he'd pointed out to her the sort of places she could go safely on her own and the ones she should avoid. He seemed to know exactly which areas were open and well-lit and which were gloomy, dotted with shrubbery that could provide hiding places for anyone with dubious intentions. It wasn't the sort of analysis that the average park stroller would make of his environment, Fiona thought. Just as someone who has almost been trapped in a fire takes an unnatural interest in fire exits forever afterwards, so only someone who imagined using a park for something other than fresh air and exercise would view their surroundings as Francis Blake viewed his. He looked at his world like a predator, not a victim.

That didn't make him a killer, however. He might be a mugger, a voyeur, a flasher or a rapist and still exhibit a similar response. But Horsforth had allowed himself to be persuaded that Blake was a killer, and he had interpreted his behaviour accordingly. That much was clear from the clinical psychologist's notes on the meeting. The conversation had been innocuous enough, but Horsforth had still managed to see what he wanted to see.

It was a realization that profoundly depressed Fiona. Any kind of objective analysis of the material was already compromised, because Horsforth's early decisions about what Blake's actions implied had dictated everything in the interaction that followed.

The meetings had continued two or three times a week. On the fourth meeting, Richards introduced the subject of Susan Blanchard's murder, in the context of terrifying things that happened to women in the city. Blake had immediately said, "I was there that day. On the Heath. I must have walked past at almost the exact time she was being raped and murdered."

Richards had pretended shock. "My God! That must have been awful."

"I didn't realize anything at the time. Well, obviously I didn't or I would have raised the alarm. But I can't help thinking if I'd chosen a slightly different route that day, if I'd gone over the rise behind the shrubbery instead of walking along the path, I'd have stumbled over her killer," he'd boasted.

It was a significant exchange, Fiona knew. But again, it was capable of a different interpretation from the conclusion Horsforth had jumped to. What it told him was that Blake was a killer desperate to talk about his crime, however obliquely. What it told Fiona was something else altogether. She made a note on her pad and continued.

By the end of the third week, Blake was beginning to turn the conversation towards sex. It was, he indicated, time to take their relationship to the next stage, beyond cinema visits and walks and meals. Richards backed off slightly, as she'd been told to do, saying she wanted to be sure they'd be compatible before she took the ultimate step of sleeping with him. It was the planned route into talk of sexual fantasy. Fiona had to concede that this had been a shrewd move on Horsforth's part, though she might have approached it in a more indirect way. But then, she wasn't a clinician. In matters like this, she had to concede her instinct was probably not the most rigorous guide.

Now it was Richards's turn to push the direction of the conversation. And she wasted no time. It wasn't that she was sexually inexperienced, she said. But she'd found herself growing quickly bored with the men she'd slept with in the past. "They're just so predictable, so conventional," she complained. "I want to be sure next time I get involved with someone, that he's got an imagination, that he'll take me places I've never been before."

Blake immediately asked her what she meant, and presumably as Horsforth had instructed her, Richards had backed off again, saying she wasn't sure she could discuss it openly in the middle of Regent's Park. She explained that she had to go out of town the next week, to a training course in Manchester, and she would write to him. "I feel a bit exposed out here," she'd said. "I can put it down on paper better. Then if you're shocked or turned off me forever, I won't have to see your face, will I?"

Blake had seemed almost amused by her alternation between suggestiveness and coyness. "I bet there's nothing you could say that would shock me," he'd said. "I promise you, whatever you want, Eileen, I can take you there. All the way there, whatever it is you want. You write me that letter tonight so I get it first thing on Monday morning, and I guarantee you'll be panting to get back to London by return of post."

Somehow, Fiona doubted it. However, there was no time now to pursue her doubts to their conclusion. Kit had packed his computer into its case, the "Fasten Seatbelts' sign was illuminated and the cabin crew were moving purposefully towards their seats for landing. Major Berrocal would be waiting for them at the arrivals gate, and a job where she was convinced she could provide useful advice was always going to take precedence over something already wrecked by someone else.

Whatever perverse fantasies Francis Blake and Erin Richards had exchanged would have to remain in the file for the time being.