'She can understand German perfectly and a certain amount of English too,' said Zena after the woman had gone. It was a warning to guard our tongues. 'Maria has worked for my aunt for over ten years.'

'But you don't talk to her in German,' said Dicky.

Zena smiled at him. 'By the time you've said tortillas, tacos, guacamole and quesadillas, and so on, you might as well add par favor and get it over with.'

It was an elegant table, shining with solid-silver cutlery, hand-embroidered linen and fine cut-glass. The meal had obviously been planned and prepared as part of Zena's pitch for a cash payment. It was a good meal, and not too damned ethnic, thank God. I have a very limited capacity for the primitive permutations of tortillas, bean-mush and chillies that numb the palate and sear the insides from Dallas to Cape Horn. But we started with grilled lobster and cold white wine, and not a retried bean in sight.

The curtains were drawn back so that air could come in through the open windows, but the air was not cool. The cyclone out in the Gulf had not moved nearer the coast, so the threatened storms had not come but neither had much drop in temperature. By now the sun had gone down behind the mountains that surround the city on every side, and the sky was mauve. Pin-pointed like stars in a planetarium were the lights of the city, which stretched all the way to the foothills of the distant mountains until like a galaxy they became a milky blur. The dining room was dark; the only light came from tall candles that burned brightly in the still air.

'Sometimes London Central can get in ahead of our American friends,' said Dicky, suddenly spearing another grilled lobster tail. Had he really spent so long thinking up a reply for Werner? 'It would give us negotiating power in Washington if we had some good material about KGB penetration of anywhere in Uncle Sam's backyard.'

Werner reached across the table to pour more wine for his wife. 'This is Chilean wine,' said Werner. He poured some for Dicky and for me and then refilled his own glass. It was Werner's way of telling Dicky he didn't believe a word of it, but I'm not sure Dicky understood that.

'It's not bad,' said Dicky, sipping, closing his eyes and tilting his head back to concentrate all his attention on the taste. Dicky fancied his wine expertise. He'd already made a great show of sniffing the cork. 'I suppose, with the peso collapsing, it will get more and more difficult to get any sort of imported wine. And Mexican wine is a bit of an acquired taste.'

'Stinnes only arrived here two or three weeks ago,' said Werner doggedly. 'If London Central is interested in Stinnes, it won't be on account of anything he might be planning to do in Silicon Valley or in the Guatemala rain forest; it will be on account of all the things he did in Berlin during the last two years.'

'Do you think so?' said Dicky, looking at Werner with friendly and respectful interest, like a man who wanted to learn something. But Werner could see through him.

'I'm not an idiot,' said Werner, using the unemotional tone but exaggerated clarity with which a man might specify decaffeinated coffee to an inattentive waiter. 'I was dodging KGB men when I was ten years old. Bernie and I were working for the department when the Wall was built in 1961 and you were still at school.'

'Point taken, old boy,' said Dicky with a smile. He could afford to smile; he was two years younger than either of us, with years' less time in the department, but he'd got the coveted job of German Stations Controller against tough competition. And – despite rumours about an imminent reshuffle in London Central – he was still holding on to it. 'But the fact is that the people in London don't tell me every last thing they have in mind. I'm just the chap chipping away at the coal-face, right? They don't consult me about building new nuclear power stations.' He poured some warm butter over his last piece of lobster with a care that suggested he had no other concern in his mind.

'Tell me about Stinnes,' I said to Werner. 'Does he come along to the Kronprinz Club trailing a string of KGB zombies? Or does he come on his own? Does he sit in the corner with his big glass of Berliner Weisse mit Schuss, or does he sniff round to see what he can ferret out? How does he behave, Werner?'

'He's a loner,' said Werner. 'He probably would never have spoken to us in the first place except that he mistook Zena for one of the Biedermann girls.'

'Who are the Biedermann girls?' said Dicky. After the remains of the lobster course had been removed, the Indian servant brought an elaborate array of Mexican dishes: refried beans, whole chillies and the tortilla in its various disguises: enchiladas, tacos, tostadas and quesadillas. Dicky paused for long enough to have each one identified and described but he took only a tiny portion on his plate.

'Here in Mexico the chilli has sexual significance,' said Zena, directing the remark to Dicky. The man who eats hot chillies is thought to be virile and strong.'

'Oh, I love chillies,' said Dicky, his tone of voice picking up the hint of mockery that was to be detected in Zena's remark. 'Always have had a weakness for chillies,' he said, as he reached for a plate on which many different ones were arranged. I glanced at Werner who was watching Dicky with interest. Dicky looked up to see Werner's face. 'It's the tiny, dark-coloured ones that blow your head off,' Dicky explained. He took a large, pale-green cayenne and smiled at our doubting faces before biting a section from it.

There was a silence after Dicky's mouth closed upon the chilli. Everyone except Dicky knew he'd mistaken the cayenne for one of the very mild aji chillies from the eastern provinces. And soon Dicky knew it too. His face went red, his mouth half opened, and tears shone in his eyes. He fought against the pain but he had to take it from his mouth. Then he fed himself lots and lots of plain rice.

'The Biedermanns are a wealthy Berlin family,' said Zena, carrying on as if she'd not noticed Dicky's desperate discomfort. 'They are well known in Germany. They have interests in German travel companies. The newspapers said the company had borrowed millions of dollars to build a holiday village in the Yucatan peninsula. It's never been finished. Erich Stinnes thought I looked just like the younger sister Poppy who's always in the newspaper gossip columns.'

There was a silence as we all waited for Dicky to recover. Finally he leaned back in his chair and managed a rueful smile. There was perspiration on his forehead and he was breathing with his mouth open. 'Do you know these Biedermann people, Bernard?' said Dicky. He sounded hoarse.

'Have an avocado,' said Werner. 'They are very soothing.' Dicky took an avocado pear from the bowl and began to eat some.

I said, 'When my father was attached to the military government in Berlin he gave old Biedermann a licence to start up his bus service again. It was one of the first after the war; it started the family fortune, I suppose. Yes, I know them. Poppy Biedermann was having dinner at Frank Harrington's the last time I was in Berlin.'

Dicky was eating the avocado quickly with his teaspoon, using it to heal the burning in his mouth. 'That was bloody hot,' he confessed finally.

'There's no way you can be sure which are hot and which are mild,' said Zena in a gentle tone that surprised me. 'They cross-pollinate; even on the same plant you can get fiery ones and mild ones.' She smiled.

'Could these Biedermann people be interesting to Stinnes?' said Dicky. 'For instance, might they own a factory that's making computer software in California? Or something like that? What do you know about that, Bernard?'

'Even if that was the case, no point in making contact with the boss,' I said. I could see that Dicky had focused on the idea of Silicon Valley and it was not going to be easy to shake him off it. 'The approach would be made to someone in the microchip laboratory. Or someone doing the programs for the software.'