'I'm getting out,' said Teacher. 'You two stay here.'

'Whatever you say.'

It was no time to start a row, but as he opened the door and got out of the driver's seat I slid out the back and into the darkness and pouring rain. Outside there was the sort of stink that roadworks always exude, the smell of disturbed earth, faeces and fuel oil. But the road here runs through a tall forest and the felling of the trees had added sap to the medley of odours. The rain soaked me to the skin before I'd taken more than two steps through the sticky mud. I kept the gun under my coat and out of sight, and watched the dim figure of Teacher walking cautiously towards the car. Some traffic swung past, driving carefully along the prescribed lane, their beams dulled by the steady rain.

While Teacher moved forward, someone got out of the car which I could now recognize as a Wartburg. The other side had taken the precaution of taping up the interior light switch. The Wartburg's interior remained dark, and the glare of the parking lights was enough to make it impossible to see whether it was a man or a woman standing there. Nearer to me – and directly behind the nearest of the big yellow machines – there was a barrier. It fenced off the deep excavations where the foundations were being extended.

'Please walk forward, one at the time,' I heard Teacher call, his uncertain German evident from only those few words.

Suddenly the full beams of the Wartburg came on. This light was hard and brilliant. It came cutting through rain that shone like glass beads, and exposed Teacher as an absurd and soaking wet gorilla. Teacher was alarmed and jumped aside into the darkness but I could still see his outline.

From the bulldozer closest to me I heard a movement, a soft metallic click that might have been the safety catch of a gun. A figure had shifted position from behind the bulldozer's tracks in order to see where Teacher had gone. I moved closer to the line of earth-moving machinery which would provide me with the sort of cover that the other side had taken advantage of. Now I could see more clearly in the darkness. There seemed to be a woman standing by the Wartburg and possibly others still inside it. The metallic sound I'd heard had come from someone standing near the barrier. It was a man holding a gun with a long silencer attached. All their attention was on Teacher.

It was like watching a performance on a fully lighted stage, its backdrop the tall trees of the immense forest while to one side there were the twin lines of traffic – one red one white – flickering away into the far distance. Now I could see Teacher, but he couldn't see the figure with the gun who was silhouetted against the mud and puddles which shone like silver in the beams of the Wartburg's headlights.

I heard a shout – almost a scream – a woman's voice, and there was someone running through the squelching mud behind me. I turned to see but our Transit van was in my field of view. Then came the first shot: the sort of soft plop you only get the first time from a gun with a brand-new silencer. It wasn't Teacher. The woman called again. She was shouting, 'Do as you were told!' In German, Berlin German.

Then came another shot, a loud report from an unsilenced gun and the smashing of glass. It was a single shot from somewhere to the left of me. Now came a confusion of darkness, pierced by pistol shots and the sudden beams of passing headlights. Traffic rumbling past gave light enough to show that the Wartburg had suffered a broken windscreen, its shattered glass scattered around like hail. In that brief flicker of light I saw Teacher standing crouched with a pistol held at arm's length, the way actors stand in TV movies about cops. I couldn't be sure whether he'd fired the shot. Had he I wondered tried to hit someone inside the car, and if so had he succeeded?

Then something came fluttering out to make a glowing pattern between me and the light of the Wartburg headlights. Until that moment I thought Tessa was still in the back of the Transit van, but there could be only one person who would go whirling through the mud, twisting and turning, oblivious to the rain and the gunfire.

Whoever shot her was standing near the front nearside wheel of the Wartburg. She was very close to the gunman when she was hit and lifted in the air. Bang. Bang. Two rounds from a shotgun floated her through the headlight beams with her skirt and draped sleeve shining and translucent yellow. As she fell back to earth she metamorphosed to crimson and the cloth wrapped round her like some beautiful flying insect that in fast playback becomes a twitching chrysalis. Illuminated by the headlights she lay full-length in the mud. The rain beat down. She moved again and then was still.

'You bastard!' said someone in English. It must have been Teacher. And then he fired, I recognized the pump-pump sound of the 9mm Browning I'd seen him carrying. Two shots very loud and very close together. One of them hit the steel frame of a big earth-moving machine, and was deflected into the sky with the piteous little cry that spent rounds give. But the other shot hit the Wartburg's near-side headlight and it went out with a secondary explosion and much hissing as the rain found the hot metal of the light.

Bang. Bang. Bang. Bang. Bang. There were men with guns in the darkness over beyond Teacher. No silencers. They returned the fire immediately. Several shots, so close together in time that they sounded almost like one. Teacher ran, stumbled and then went down with a loud scream. I could just see him in the gloom beyond the light provided by the Wartburg's solitary beam. He writhed and shouted, hugging himself with both arms like a man trying to escape from a strait jacket of pain.

But under cover of the attention he was getting I was able to slide round the back of the bulldozer and scramble up on to the wide track. The blade was elevated and I used it for cover as I climbed as high as I could.

I was rewarded with a view of the whole site. More traffic moving slowly past in single file provided light to see the wide trench of the excavations, the line of earth-moving machines and at the end of it the Wartburg. In the centre of the stage there was the Transit van parked askew and to the left of it Teacher's body. Two men came from the direction of the shots and stood over Teacher. One of them prodded the body with the toe of a shoe. There was no sign of life. 'It's all safe now,' he said. I recognized the voice of Erich Stinnes.

From behind the Wartburg there came the woman. She walked carefully so as not to put her shoes into the worst of the muddy pools. It was Fiona, my wife.

'How many did they send?' said one of the men.

'A man and a woman,' said Stinnes. 'They are both dead.' Fiona walked past Tessa's body and looked down at Teacher without giving any sign of recognizing him. I realized then that she'd not recognized her sister either. Stinnes turned to look at the Transit van. He was probably considering the smashed windscreen of the Wartburg and what it would be like to be behind it driving through the rain that was still falling.

At that moment I had many alternatives. I suppose the textbook would have wanted me to negotiate with them, but I wasn't a dedicated reader of textbooks and training manuals, which is the principal reason that I was still alive. So I raised my big revolver and resting the barrel on the dozer's heavy steel blade – the sort of position considered unsporting by the instructors supervising the Department's outdoor firing range – I fired at the one who was farthest away, aiming for the centre of the body. The heavy Webley round hit him like a sledge-hammer slamming him into the darkness where he remained still and silent. The second man-the one called Stinnes-stepped back in alarm but his training overcame his fear and, without seeing me, he raised his gun and fired three times, aiming in my general direction. The bullets buzzed past my head and one plucked at my coat. It was the right thing to do: the prevailing theory being that your adversary stops shooting and seeks cover. But my reactions were far too slow for such theories and by that time I'd hit him with my second round. It struck him in the neck.