Roberta stared at Ben. Her face was tight. She shoved him angrily. He didn’t react. She thumped his chest. ‘Who the fuck are you?’

He saw the bright red dot pass across her forehead a third of a second before he grabbed her collar and wrenched her violently to one side.

Then, all at once, the laser-sighted rifle across the river was tearing chunks of masonry out of the wall. Three-shot burst, fully automatic fire. One of the shots went straight through the bald man’s head. His skull burst apart, spraying blood across Roberta. His falling body crashed against hers and took her down with him as it crumpled to the ground. Her legs kicked from under the corpse as she screamed in panic.

Ben had already seen the glint of the rifleman’s scope lens fifty metres away and he was returning fire. The Browning flashed and kicked in his hand. The sniper let out a stifled cry, tumbled from his perch and splashed into the river. His AR-18 assault weapon clattered to the ground.

Two more men were running up the riverbank towards them. Pistols in their hands. A bullet went past Ben’s ear and another sang off the wall next to him.

He raised the pistol. Calm. Focus centre of target. The trigger breaks without conscious thought. Two double-taps in rapid succession, bringing both men down in just over a second. Their bodies slumped to the ground and lay still, black shapes in the moonlight.

Ben hauled the dead man off Roberta and kicked the body to one side. Half of the bald crown was missing. Her clothes and hair were soaked in blood. ‘Are you hurt?’ he asked urgently.

She staggered to her feet. Her face was pale, and the next thing she was spewing her guts out against the wall. Ben heard police sirens in the distance, several of them, their high-pitched wails rising and falling in and out of phase with each other, approaching fast. ‘Come on.’

She wasn’t responding. There was no time to reason with her. He put his arm around her waist and half-carried her along the quayside to the flight of steps leading up to the street.

At the top of the steps she seemed to regain her senses. She struggled in his grip and tore away from him. He yelled her name. But she was running frantically the opposite way, straight towards the sound of the sirens. Any moment now the police would be on top of them. ‘Get away from me!’ she screamed at him. He chased her, tried to take her arm, reasoning with her. ‘Don’t touch me!’ She staggered away from him.

Flashing blue lights were appearing at the end of the street among the scattered traffic. Ben had no choice. He had to let her go. At least she’d be safe in police hands, and within the hour he’d be out of the city and far away. With a last glance at her, he turned and started running back towards the Peugeot.

Roberta was staggering dazed up the middle of the road. A couple of cars honked, swerving to avoid her. Ben watched from a distance as the police car skidded to a halt beside her. Three cops got out, took one look at the shocked, bloody state of her and connected her right away with the reported shooting. More sirens were shrieking in the distance-three, maybe four more cars racing to the scene.

They were putting her into the back of the police car when the black Mitsubishi pulled up next to them.

Ben was a hundred metres away when he saw the Mitsubishi’s doors fly open and the two men with sawn-off pump shotguns step out. They blasted the cops before either of them had a chance to draw a pistol. Roberta was crawling out of the back as they walked round the side of the police car, racking the slides on their shotguns.

The Peugeot slammed into the nearest one, sending him flying in a broken heap. Ben fired a shot through the open window at the other, who ducked for cover behind the police car and then ran for it. Ben threw open the door, hauled Roberta in and skidded off over the bridge and away, just in time to screech around the nearest bend down a sidestreet before the wailing fleet of police arrived on the scene.

Two hours earlier

During the Nazi occupation of Paris the sprawling honeycomb of austere rooms and dark corridors had been used as a Gestapo prison and interrogation centre. Nowadays the enormous basement beneath the police HQ housed, among other things, the forensic lab and morgue. It was as though the place couldn’t shake off its gruesome heritage.

Luc Simon was standing with the forensic pathologist, the tall thin white-haired Georges Rudel, in a stark neon-lit examination room. On the slab in front of them, a corpse lay covered in a white sheet. Only the feet were visible, protruding from underneath, pallid and cold. A label dangled from one toe. Simon wasn’t a squeamish man but he fought the urge to look away as Rudel casually peeled back the sheet far enough to uncover the corpse’s head, neck and chest.

They’d cleaned Michel up since the last time Simon had seen him, but he still wasn’t a pretty sight. The bullet had entered under the chin, carved its wound channel up behind the face, taking most of it away before exiting through the top of the head. Just one eye remained, sitting in its socket like a hard-boiled egg with a pupil that seemed to stare right at them.

‘What’ve you got for me?’ Simon asked Rudel.

The pathologist pointed at the mess of Michel’s face. ‘Damage here is all consistent with the bullet found in the ceiling,’ he said, speaking mechanically as though dictating a report. ‘Entry wound here. Weapon was held against the upper chest with the muzzle in loose contact with the lower jaw. Edges of the entry wound are burned from combustion gases and blacked with soot. The weapon was a Smith and Wesson revolver, three inch barrel,.44 Remington Magnum. The powerful calibre accounts for the amount of bone and tissue damage.’

Simon tapped his foot impatiently. He hoped that this was leading somewhere.

‘Typically that calibre uses much slower-burning powder than you get with semi-auto rounds like the nine millimetre,’ Rudel went on matter-of-factly ‘That means you get a lot of unburnt residue, especially with a short barrel. Doesn’t burn so clean.’ He pointed. ‘You can see it all here, embedded in the skin. Also here down the neck.’

Simon nodded. ‘OK, so what are you telling me?’

Rudel turned to look at him with bleary eyes. ‘The victim’s prints are on the stocks and the trigger of the weapon. So we know he fired the shot without gloves.’

‘He was found still clutching the gun. No gloves. We know that. Are you going to cut to the chase before one of us dies?’

Rudel ignored the sarcasm. ‘Well, this is what I find perplexing. With all this mess of unburnt powder I’d expect to find a lot of it on the gun hand, as well as the normal chemical discharge that blows back when the weapon is fired. But this man’s hands are clean.’

‘You’re sure about this?’

‘Quite sure-it’s a simple swab test for residue.’ Rudel reached down and lifted a pale lifeless arm out from under the sheet. ‘See for yourself.’

‘You’re saying he didn’t fire the shot.’

Rudel shrugged, and let the dead hand flop back down by the corpse’s side. ‘Only thing on this man’s hands, apart from the usual sweat and grease, are some traces of oily fish. Pilchard, to be precise.’

It struck Simon as absurd, and he laughed. ‘You ran a test for pilchard?’

Rudel looked at him coldly. ‘No, there was a half-opened tin of it on his kitchen table, next to a cat’s feeding dish. Now, all I’m saying is, who would blow their brains out in the middle of feeding their cat?’

The boy was jerked semi-conscious as they dragged him off the hard bunk. He heard voices around him, the clang of metal doors and the jangling of keys. Sounds echoed in the empty space. A swirl of lights blinded him through his confusion. A sudden lancing pain in his arm made him wince.