'There is.' Halder pointed to a nearby surveillance camera. 'Think of it as a new kind of togetherness.'

Halder had recovered from his nervousness outside the Bachelet house, and was ready to humour me and resume his role as tour guide to an obsession. He opened his envelope of photographs, waiting for me to calm myself. By abandoning the conspiracy theory I had returned to earth, a hard landing that had wrecked my hopes of finding a larger explanation for David Greenwood's psychotic behaviour. But the authority of the murder photographs was overwhelming. A violent rage had written itself across the blood-stained walls, a death warrant signed in fragments of bone and gristle.

'All set, Mr Sinclair? Good… I'll take it slowly.' Halder spoke in a low, unemotional voice, as if describing a minor traffic incident. 'The third person to die was Professor Berthoud, chief pharmacist at the clinic. An inside security camera caught Greenwood entering the lobby at 7.52. No weapon was visible, but we assume he carried the rifle under his white coat.'

'The metal detectors didn't pick it up?'

'None are installed. This is a hospital. Metal objects are everywhere – emergency trolleys, hip replacement pins, oxygen cylinders…'

'Fair enough. Go on.'

'Berthoud was in his private office in the pharmacy on the sixth floor, next to the strongroom where all the drugs at Eden-Olympia are held. He was sitting at his desk when Greenwood fired at him through the outer glass door.'

'Why didn't he go straight in?'

'The door was electronically locked from Berthoud's desk. It gave access to the office and a side corridor to the drugs room.'

'Berthoud would have buzzed him in.'

' Greenwood needed surprise. He must have known how shaky he was starting to feel. Berthoud might have guessed something was wrong and alerted security.'

'And Wilder Penrose?' I asked. ' Greenwood wounded him.'

'He was in the corridor, coming back from the drugs room. He probably caught a look at the rifle barrel, stepped back and was cut by the flying glass.'

'But Greenwood didn't see him, or he would have finished him off. Why didn't Greenwood look for Penrose in his office?'

'Maybe he did. But he had to move fast. Security would start closing around him at any moment. From now on he was after targets of opportunity.'

'That makes sense.' I stared at the surveillance camera near the Range Rover, realizing that Halder and I were being watched in the security building. Our battlefield tour had almost certainly been authorized by Pascal Zander. 'Anyway, imagine Greenwood 's state of mind. He's just killed three people. He can't think coherently, but he knows he has to make it to the next target. One thing bothers me – why didn't Penrose raise the alarm?'

' Greenwood locked the outer doors when he left, trapping Penrose in the corridor. The security people found him an hour later, practically unconscious, trying to tourniquet his arm with his coat sleeves. He only just made it.' Halder shook his head in genuine admiration. 'You need to be a psychiatrist to cope with something like that.'

'But no one heard anything? Isn't that a little strange?'

'This is a hospital,' Halder again reminded me. 'The walls are well insulated. So the patients don't hear machinery or…'

'… other patients in pain. Are there any photos?'

'Just one.' Halder's hands were on the steering wheel, and he made an effort to control his fretting fingers. He wiped the thin film of sweat from his face, and then opened the manila envelope.

'I don't know if it says much.'

I held the photograph against the instrument panel. The pharmacist's office was a windowless room filled with metal cabinets and bookshelves stacked with pharmaceutical directories, drug manuals and updated regulations of the French Ministry of Health. Professor Berthoud sat at his desk, face and torso turned to the camera, as if noticing someone at the glass door. He was a plump, suave-looking man in his late forties, with a neat moustache and even neater desk, in the centre of which lay a metal suitcase. Berthoud had removed the jacket of his dove-grey suit, and wore a striped shirt and paisley tie. He had yet to put on his lab coat, suggesting that he was about to carry out a private task before taking up his official duties.

Whatever the task, he had not been able to see it through. His head and shoulders rested against the ventilation shaft behind his desk. His mouth was open, as if he had been trying to call to someone in the next room. His tie hung vertically from his tight collar, with the small knot of a punctilious and pedantic man.

I could see the bullet hole that punctured one of the whorls of the paisley pattern. Blood ran onto his lap, flowing down one leg to form a pool between his feet, but the neatness of this trimly professional man was preserved in death. His cheeks had slipped down his face, losing their hold on the underlying muscles, yet his hands remained calmly on the desk, protecting a plastic sachet filled with a chalk-like powder. A dozen or so sachets lay inside the suitcase.

I pointed to a set of electronic scales on the desk. 'He was weighing something. What exactly was in the sachets?'

Halder pinched his nostrils, and shrugged with studied vagueness.

'I guess… pharmaceuticals?'

'But what kind? It looks as if Greenwood walked in on a drug-running operation.'

'Mr Sinclair… a lot of white powders are moving around. Some have Max Factor printed on them. Industrial chemicals, detergents used to clean out dialysis machines…'

'And all in special packs with the manufacturer's brand-name and seal. Why would Berthoud be using the scales?'

Halder leaned against his headrest and turned to watch me.

'You think the powder was cocaine or heroin?'

'It looks like it. Something illicit was going on. And Penrose must have known about it.'

'You ought to talk to him, Mr Sinclair.'

'I will, when the time is right. I'm surprised the investigating judge wasn't more interested. But why would a man as senior as Berthoud risk everything on a small consignment of illegal cocaine, when he could legitimately order the stuff by the hundredweight? This suitcase and the scales are amateurish. It's as if he was playing a game out of sheer bravado.'

Halder nodded approvingly, pleased by my progress through the obstacle course. 'Go on, Mr Sinclair…'

'How is it that Greenwood arrived just as Berthoud is getting his shipment ready? That's quite a coincidence. And what was Penrose doing in the drug store?' I handed the photograph back to Halder. 'Where did these photos come from?'

'The Cannes police. Their eyes aren't as sharp as yours.' He started the engine of the Range Rover. 'We ought to move on. Ghosts are walking around Eden-Olympia…'

The TV centre's car park was full, and Halder paused in an access lane fifty yards from the mirror-clad building. The international soccer results and the digests of German, Japanese and French news bulletins were broadcast from the basement, a maze of airless recording studios and edit suites. Here I had once lost myself after being interviewed about my first impressions of Eden-Olympia. Wandering through the wrong doors, I found myself an involuntary guest on a wine-tasting programme run by two strong-minded Swiss women.

'The TV centre, Mr Sinclair,' Halder told me. 'It's where I came in…'

I waited for him to drive towards the entrance, but he was staring in an oddly fixed way at the revolving doors. The muscles of his face had tightened, pulled by a set of interior strings he could barely control.

'Halder, can we park in the shade?' I pointed to the awning over the entrance. 'It's getting hot out here, in all senses…'

'Not yet.' Halder opened his door and touched the tarmac with his foot. 'This is where I parked on May 28. Right here. A kind of personal ground zero, Mr Sinclair.'