Put a final question, to see if it was just paranoia: let him tell me. 'Bian, can you think why they would watch for anyone asking for insulin?'

He seemed a little surprised. 'I would think because they know our guest has need.'

Had need. And was somewhere in Lhasa.

He stood there, Bian, holding the small brown-paper packet of aspirin and some money, the change; he watched me with pain in his eyes: it was perhaps his 'guest's' karma to be found and taken away. The wind whipped at his worn soiled robes.

'Where else,' I asked him, 'could I find insulin? Not the hospital or the clinics — would an apothecary stock it?'

'Perhaps I'll try-'

'No.'

It was too dangerous now; it needed professional handling. I asked him for the prescription and told him to offer the money at one of the altars at the monastery and add the aspirin to their medical supplies; then I walked with my back to the wind and sat on a broken bench in a little park and worked on things and came up with the essentials: that unless there was another diabetic on the run the KCCPC either knew or suspected that Xingyu Baibing was here in Lhasa and were closing in; that it would take time to signal Pepperidge because the telephones here weren't very good and you had to go through an operator and I didn't know Mandarin or Tibetan; and that Xingyu had got to have insulin before noon and there was only one way I could get it for him and the risk was appalling.

The snakes were alive. I think.

It doesn't need saying, surely, that in any mission, whatever the objective, whatever the target, the one primordial requirement is to stay clear of the opposition, particularly if the opposition is not a private cell but the entire security network of the host country: police, secret police, civil and military intelligence. The one primordial requirement is to stay clear of them and get back across the frontier with a whole skin and the documents or the tapes or the defector or the blown spook who's going to die out there if you don't, die out there or finish up under the five-hundred-watt bulb without a capsule and blowing the roof off London.

They weren't moving. They were just a lot of coloured spirals curving around the inside of the big glass jar, their little black eyes open, but that didn't mean anything, we go on watching life after death, don't we, until someone closes the lids. But in any case I was disgusted. I can't stand those bloody things.

The apothecary peered at the grubby bit of paper. The light was bad.

Of course there are times when we can't for some reason stay clear of the opposition and then all we can do is to pop it and protect the mission or get clear again, bloodied but unbowed, so forth. Then there's third situation that comes up sometimes but thank God not very often: it's where the only way to keep the mission going and hope to survive and reach the objective is to set yourself up as a target and wait for them to shoot and that was what I was doing now.

One of them was moving, its small head dropping and swinging around inside the jar with the black forked tongue flickering, and I looked away, the flesh creeping, they've got no bloody feet anywhere, those things, all they can do is writhe.

'Insulin,' the old man nodded, peering at the bit of paper.

'Yes,' I said.

The decorated canopy cracked above the shopfront in the wind, and the man behind me fell prone again onto the flat of his hands, facing toward the temple farther along. A dog sniffed at his rags.

I'd tried two other apothecaries but at the first one the girl had just looked at the prescription for a long time and finally shaken her head and flashed all her gold teeth and at the second one the man said in quite good English that he was disappointed at not being able to oblige me but that I should try the one around the corner, toward the Barkhor plaza. I was there now.

There were other things, apart from the snakes: rows of bottles and bowls of herbs and a huge dried starfish and an armadillo; but there was a shelf of phials and flagons with typed labels, and a small poster with Bayer at the top. I'd been trying apothecaries in the hope of making a deal; they owned their own places and could break the rules if they wanted to, and I put the price of their wanting to at about one hundred yen.

The old man was raising his head slowly, looking up from the prescription and bringing his eyes to focus directly on mine with his face close; and in his eye there was a warning. Then their focus shifted, and it was quite clear that he was looking behind me, through me, at something else.

I said softly, 'Police?'

He nodded, pleased that I'd understood. 'If sell you this, must tell them. It is order.' Below his bald pate his brows made furrows as many as the armadillo's 'Perhaps it better you leave now.'

I heard the man outside fall flat on his hands again in obeisance to the gods of the temple; he'd moved another few yards. I could hear other sounds, mostly voices from the people at the vegetable stalls opposite and the rumbling of ironbound wheels and the dragging of harness. The dog that had sniffed at the pilgrim's rags now sniffed at my combat boots. Farther along the street there were prayer bells ringing, tuneless but with a steady rhythm. I listened carefully, analyzing the environment, because in a moment I was going to cross the line and present myself to the opposition, because I had no choice.

'I must have the insulin,' I told the apothecary 'It's urgent.' He watched me steadily, his eyes bright with intelligence, but it was obviously beyond him to understand me. 'It doesn't matter,' I told him, 'about the police.'

There was no point in pushing money at him as a bribe. In the last few minutes I'd come to know him well enough; he was an apothecary, a man of high standing in his community, a man, by his art, of great responsibility, and if he decided to report me to the police he would do it as a point of honor, the police being his enemy here; his goodwill would not be for sale.

'You understand,' he asked me, his eyes grave, 'you understand what is the truth of this thing?'

'Yes. But the police are not looking for me. I shall have no trouble.'

He lifted his hands, their skin like crumpled silk, and let them fall gracefully. 'Ah. Then it is good.'

It was a long time, minutes, before he'd filled in the form, peering again at the prescription. 'And the name? The name is not clear.'

'Xiao Dejian,' I said and spelled it for him. He wrote it down, using a pen with ink the colour of blood. Then I gave him some money and he gave me change and I took the flat packet of ampoules and returned his bow and walked through the strange leaden light of the morning, hearing the sudden shout and ignoring it because it was only in my mind, the nerves shimmering in the system with a feeling of cold light and the scalp drawn tight, because I had staked the whole of the mission on one throw, on the logical assumption that if the KCCPC were watching the clinics and the apothecaries for anyone buying insulin they wouldn't make an arrest but would simply follow.

They were not clods in the Kuo Chi Ching Pao Chu. A cloddish intelligence service would have given orders to have me arrested and thrown into a cell and interrogated, but these people knew how long the odds are against getting information out of a trained agent; it's not an exact science, and you can beat a man into a kind of stupor where he himself wouldn't know the truth from a lie, or you can push him beyond the point when he can tell you anything at all.

They thought or they knew that Dr Xingyu Baibing was in Lhasa, and the odds were better that I could lead them to him now.