'And Eden-Olympia is happy with that?'

'As long as they stay well outside the business park. In fact, it does everything it can to help…'

After exchanging seats, we left the garage. I told Halder that I would walk back across the park, half-hoping that I might find some clue to Greenwood 's return route. Halder drove at a cautious pace down the spiral ramp, but I hesitated before stepping from the car.

'Halder – you're safe to drive? Think of that promotion.'

'It was hot on the roof, Mr Sinclair. I humiliated myself a little. That's all. I can give you a lift.'

'I'll walk. There's a lot to think about, most of it grim.' I gazed at the lines of office buildings rising from the park like megaliths of the future. 'Corbusier's Cité Radieuse – I'm sorry David Greenwood wasn't happy here.'

'He was pretty confused. At the end all his shadows ran up to greet him.'

'Even so.' Reluctant to leave Halder, I pointed to the manila envelope. 'I don't think he was confused. Those pictures show the murders were very carefully planned. Greenwood must have guessed that the victims would be photographed. Each murder scene is a kind of tableau. Bachelet with his crack pipe and stolen jewellery. Berthoud with his suitcase of heroin. Vadim and the kiddie porn. Each photograph isn't Greenwood 's crime scene – it's theirs.'

'Kiddie porn, drugs, fascist ideas… not exactly serious crimes these days.'

'But serious enough. And only the tip visible above the water. These bowling clubs, and the road accidents… something deeply criminal has taken root here. The senior people at Eden-Olympia think they're lords of the chateau, free to ride out and trample down the peasantry for their own amusement.'

'You're wrong, Mr Sinclair.'

'I can't believe Greenwood killed himself.' Ignoring Halder, I pressed on. 'I'm sure he gave himself up. He'd killed seven people and he needed to explain why. He wanted to go to trial.'

'That's a dangerous theory. Keep it to yourself.'

'He knew the police photographs would prove his case. Other witnesses would come forward and confirm what he'd seen. But he hadn't counted on the enormous power that Eden-Olympia controls, or the total ruthlessness. Somewhere near here, probably only a few hundred yards away, he surrendered to the security people chasing him. Almost certainly, they took him back to the villa and executed him there.'

'No.'

'Frank?'

'They didn't.' Halder spoke so quietly that I could scarcely hear him above the engine. He composed himself, waiting for the muscles of his face to calm themselves. 'Take it from me, he wasn't executed.'

'No? Then why are there no photos of Greenwood 's body? Paris Match, Der Spiegel, the London tabloids – they've never printed a single one. I suspect they'd show a few bullets in the back.'

'They don't.' Halder spoke tersely, swaying against the steering wheel as if about to faint again. 'Believe me, Mr Sinclair.'

'Have you seen the photos?'

'I don't need to. I was there when Greenwood died.'

'Frank? You were with the security unit who tracked him down?'

Halder waved me away, reciting his words like a familiar private mantra. ' Greenwood went down fighting… he'd taught himself to handle a firearm. He wasn't afraid at the end, and he didn't care if it all came out. Something went wrong for him at Eden-Olympia, and he tried to put it right. He wasn't interested in what anyone thought about him…'

'Frank… wait. Who shot him?'

I tried to climb back into the car, but Halder closed the passenger door. He thrust the envelope of photographs through the open window, his face fully calm for the first time that day.

'I shot him, Mr Sinclair. I was the rookie here and they told me what to do. I was so scared I couldn't think. David Greenwood was the only man I liked in the whole of Eden-Olympia. And I shot him dead.'

Fanning myself with the manila envelope, I watched the Range Rover roll away beneath the plane trees. Its dark paintwork moved from light to shade, at times becoming almost invisible, a conjuring trick with the eye that seemed part of the huge illusion created by Eden-Olympia. I admired Halder for making his confession, and felt concerned for him, but his motives were just as checkered. Zander and Wilder Penrose were using this moody young black to keep me primed with fresh information, steering me from one loose paving stone to the next, confident that I would peer into every murky space.

But Halder had an agenda of his own. He had used the murder tour to provoke himself, preparing the emotional ground for his confession, but his anger had been addressed to Eden-Olympia.

I could well imagine the sly pleasure that Penrose had taken in assigning the killer of Jane's former colleague and possible lover to our security detail. I remembered Halder bouncing the beach ball across the pool and then spitting into the water, not far from the pumphouse where Greenwood had probably collapsed after making his way back to the villa from the Siemens building.

Halder would have walked towards him, the novice in his crisp new uniform, thinking of his salary cheque and pension plan, and then hearing the command to shoot and kill. Eden-Olympia had used him, but Greenwood 's death had given him a celebrity that he in turn had begun to exploit.

Yet Greenwood, according to Halder, had fired back in the seconds before he died. No doubt Halder had flinched, but his nerve had held, and he had done as he was told. I looked up at the roof of the car park, where the security guard leaned on the parapet, a hand cupped over his eyes as he followed Halder's Range Rover across the park. He saluted smartly, without a hint of irony, displaying the same deference towards Halder shown by all the security men. Only the killing of David Greenwood would have earned the respect of these crude and racist men.

I stepped from the car-park lift onto the overheated roof, a cockpit of sun and death. In the mirror curtain-walling of the office building I could see myself reflected like an unwary tourist who had strayed through the wrong door into the danger-filled silences of a bullring. The guard had withdrawn across the bridge into the cool shadows of the lobby. I waved to him, and strolled to the parapet, pretending to gaze across the green heights of the business park.

I counted three more bullet holes in the parapet, each reamed out and filled with a plug of Ciment Fondu, then covered with a finish of coarse sand. Six bullets had been fired, the full load of a large-calibre revolver discharged at close range.

Leaving the roof, I made my way down the stairs to the welcome shade of the deck below. I moved through the parked cars to the south-east corner, where the drainage pipe emerged from the roof.

A metal clamp locked the plastic tube to the vent above my head, its funnel polished by the abrading tool. The junction was six feet away, well beyond my reach even if I stood on a car roof, but a second clamp was a few inches from the floor, securing the down-pipe to the vertical segment below it. I took out my car keys and searched for a flat edge, then began to turn the metal bolt, loosening the joint between the sections of piping.

Steps sounded from the staircase, the rapid heels of a young man in a hurry. A Japanese executive in a blue suit, chrome-trimmed briefcase in hand, strode across the concrete deck. I crouched behind the rear wing of a nearby Saab, and waited while the Japanese stepped into his sports car. After checking his teeth and tongue in the rear-view mirror, he started the engine and reversed from the parking space, emitting a roar of confidence-building exhaust.

His noisy gear changes masked the sound of tearing plastic as I wrenched the drainage pipe from its roof mount. I laid the tubular section on the floor and pressed my hand into the upper end, then scraped the inside surface with my keys.