He stood at the mouth of the avenue, gazing into the ranks of beech trees as they sank away from him like a retreating army into the mist. The darkness had departed reluctantly, leaving an indoor gloom. It could have been dusk already : tea-time in an old country house. The street lights either side of him were poor candles, illuminating nothing. The air felt warm and heavy. He had expected police still, and a roped-off area. He had expected journalists or curious bystanders. It never happened, he told himself, as he started slowly down the slope. No sooner had I left the scene than Vladimir clambered merrily to his feet, stick in hand, wiped off the gruesome make-up and skipped away with his fellow actors for a pot of beer at the police station.

Stick in hand , he repeated to himself, remembering something the Superintendent had said to him. Left hand or right hand? 'There's yellow chalk powder on his left hand too,' Mr Murgotroyd had said inside the van. 'Thumb and first two fingers.'

He advanced and the avenue darkened round him, the mist thickened. His footsteps echoed tinnily ahead of him. Twenty yards higher, brown sunlight burned like a slow bonfire in its own smoke. But down here in the dip the mist had collected in a cold fog, and Vladimir was very dead after all. He saw tyre marks where the police cars had parked. He noticed the absence of leaves and the unnatural cleanness of the gravel; What did they do? he wondered. Hose the gravel down? Sweep the leaves into yet more plastic pillowcases?

His tiredness had given way to a new and mysterious clarity. He continued up the avenue wishing Vladimir good morning and good night and not feeling a fool for doing so, thinking intently about drawing-pins and chalk and French cigarettes and Moscow Rules, looking for a tin pavilion by a playing field. Take it in sequence, he told himself. Take it from the beginning. Leave the Caporals on their shelf. He reached an intersection of paths and crossed it, still climbing. To his right, goal-posts appeared, and beyond them a green pavilion of corrugated iron, apparently empty. He started across the field, rain-water seeping into his shoes. Behind the hut ran a steep mud bank scoured with children's slides. He climbed the bank, entered a coppice, and kept climbing. The fog had not penetrated the trees and by the time he reached the brow it had cleared. There was still no one in sight. Returning, he approached the pavilion through the trees. It was a tin box, no more, with one side open to the field. The only furniture was a rough wood bench slashed and written on with knives, the only occupant a prone figure stretched on it, with a blanket pulled over his head and brown boots protruding. For an undisciplined moment Smiley wondered whether he too had had his face blown off. Girders held up the roof; earnest moral statements enlivened the flaking green paint. 'Punk is destructive. Society does not need it.' The assertion caused him a moment's indecision. 'Oh, but society does ,' he wanted to reply; 'society is an association of minorities.' The drawing-pin was where Mostyn said it was, at head height exactly, in the best Sarratt tradition of regularity, its Circus-issue brass head as new and as unmarked as the boy who had put it there.

Proceed to the rendezvous , it said, no danger sighted.

Moscow Rules, thought Smiley yet again. Moscow, where it could take a fieldman three days to post a letter to a safe address. Moscow, where all minorities are punk.

Tell him I have two proofs and can bring them with me ...

Vladimir's chalked acknowledgement ran close beside the pin, a wavering yellow worm of a message scrawled all down the post. Perhaps the old man was worried about rain, thought Smiley. Perhaps he was afraid it could wash his mark away. Or perhaps in his emotional state he leaned too heavily on the chalk, just as he had left his Norfolk jacket lying on the floor. A meeting or nothing ... he had told Mostyn... Tonight or nothing ... Tell him I have two proofs and can bring them with me ... Nevertheless only the vigilant would ever have noticed that mark, heavy though it was, or the shiny drawing-pin either, and not even the vigilant would have found them odd, for on Hampstead Heath people post bills and messages to each other ceaselessly, and not all of them are spies. Some are children, some are tramps, some are believers in God and organizers of charitable walks, some have lost pets, and some are looking for variations of love and having to proclaim their needs from a hilltop. And not all of them, by any means, get their faces blown off at point-blank range by a Moscow Centre assassination weapon.

And the purpose of this acknowledgement? In Moscow, when Smiley from his desk in London had had the ultimate responsibility for Vladimir's case - in Moscow these signs were devised for agents who might disappear from hour to hour; they were the broken twigs along a path that could always be their last. I see no danger and am proceeding as instructed to the agreed rendezvous , read Vladimir's last - and fatally mistaken - message to the living world.

Leaving the hut, Smiley moved a short distance back along the route he had just come. And as he walked, he meticulously called to mind the Superintendent's reconstruction of Vladimil's last journey, drawing up his memory like an archive.

Those rubber overshoes are a Godsend, Mr Smiley, the Superintendent had declared piously : North British Century, diamond-pattern soles, sir, and barely walked on - why, you could follow him through a football crowd if you had to!

'I'll give you the authorized version,' the Superintendent had said, speaking fast because they were short of time. 'Ready, Mr Smiley?'

Ready, Smiley had said.

The Superintendent changed his tone of voice. Conversation was one thing, evidence another. As he spoke, he shone his torch in phases onto the wet gravel of the roped-off area. A lecture with magic lantern, Smiley had thought; at Sarratt I'd have taken notes : 'Here he is, coming down the hill now, sir. See him there? Normal pace, nice heel and toe movement, normal progress, everything above board. See, Mr Smiley?'

Mr Smiley had seen.

'And the stick mark there, do you, in his right hand, sir?' Smiley had seen that too, how the rubber-ferruled walking stick had left a deep round rip with every second footprint. 'Whereas of course he had the stick in his left when he was shot, correct? You saw that, too, sir, I noticed. Happen to know which side his bad leg was at all, sir, if he had one?'

'The right,' Smiley had said.

'Ah. Then most likely the right was the side he normally held the stick, as well. Down here, please, sir, that's the way! Walking normal still, please note,' the Superintendent had added, making a rare slip of grammar in his distraction.

For five more paces the regular diamond imprint, heel and toe, had continued undisturbed in the beam of the Superintendent's torch. Now, by daylight, Smiley saw only the ghost of them. The rain, other feet, and the tyre tracks of illicit cyclists had caused large parts to disappear. But by night, at the Superintendent's lantern show, he had seen them vividly, as vividly as he saw the plastic-covered corpse in the dip below them, where the trail had ended.

'Now ,' the Superintendent had declared with satisfaction, and halted, the cone of his torchbeam resting on a single scuffed area of ground.

'How old did you say he was, sir?' the Superintendent asked.

'I didn't, but he owned to sixty-nine.'

'Plus your recent heart attack, I gather. Now, sir. First he stops. In sharp order. Don't ask my why, perhaps he was spoken to. My guess is he heard something. Behind him. Notice the way the pace shortens, notice the position of the feet as he makes the half-turn, looks over his shoulder or whatever? Anyway he turns and that's why I say "behind him". And whatever he saw or didn't see - or heard or didn't hear - he decides to run. Off he goes, look!' the Superintendent urged, with the sudden enthusiasm of the sportsman. 'Wider stride, heels not hardly on the ground at all. A new print entirely, and going for all he's worth. You can even see where he shoved himself off with his stick for the extra purchase.'

Peering now by daylight, Smiley no longer with any certainty could see, but he had seen last night - and in his memory saw again this morning - the sudden desperate gashes of the ferrule thrust downward, then thrust at an angle.

'Trouble was,' the Superintendent commented quietly, resuming his courtroom style, 'whatever killed him was out in front, wasn't it? Not behind him at all.'

It was both, thought Smiley now, with the advantage of the intervening hours. They drove him, he thought, trying without success to recall the Sarratt jargon for this particular technique. They knew his route, and they drove him. The frightener behind the target drives him forward, the finger man loiters ahead undetected till the target blunders into him. For it was a truth known also to Moscow Centre murder teams that even the oldest hands will spend hours worrying about their backs, their flanks, the cars that pass and the cars that don't, the streets they cross and the houses that they enter. Yet still fail, when the moment is upon them, to recognize the danger that greets them face to face.

'Still running,' the Superintendent said, moving steadily nearer the body down the hill. 'Notice how his pace gets a little longer because of the steeper gradient now? Erratic too, see that? Feet flying all over the shop. Running for dear life. Literally. And the walking stick still in his right hand. See him veering now, moving towards the verge? Lost his bearings, I wouldn't wonder. Here we go. Explain that if you can !'

The torchbeam rested on a patch of footprints close together, five or six of them, all in a very small space at the edge of the grass between two high trees.

'Stopped again,' the Superintendent announced. 'Not so much a total stop perhaps, more your stutter. Don't ask me why. Maybe he just wrong-footed himself. Maybe he was worried to find himself so close to the trees. Maybe his heart got him - if you tell me it was dicky. Then off he goes again same as before.'

'With the stick in his left hand,' Smiley had said quietly.

'Why? That's what I ask myself, sir, but perhaps you people know the answer. Why? Did he hear something again? Remember something? Why - when you're running for your life - why pause, do a duck-shuffie, change hands and then run on again? Straight into the arms of whoever shot him? Unless of course whatever was behind him overtook him there, came round through the trees perhaps, made an arc as it were? Any explanation from your side of the street, Mr Smiley?'