'Who are you?'

'Joost is my name. I belong to an organisation, the Green Knights. You've heard of us?'

Ellie mumbled something noncommittal.

'We're an environmental group. You know the old story, right? The Green Knight cuts off your head if you tell lies or do bad things? We do that for companies.'

'You're spying on Talhouett?

He tapped the camera. 'Doc.u.menting them.'

'Then we're on the same side.' Cautiously, Doug reached into the backpack and pulled out the Talhouett file. The muzzle followed him all the way. Doug tossed it on to the floor between them.

'That's their file on this place.'

Joost crouched, angling the gun towards them, and leafed through the file. Under the camouflage and dirt, Ellie saw his face soften.

'This is gold. Geological surveys, invoices, environmental reports. Risk a.s.sessments.'

'Risk of what?' Ellie said. 'What's happened here? Where did the lake go?'

The gun tilted down a bit. 'Hydraulic fracturing.' He saw it meant nothing to them. 'Talhouett have a coal mine here, OK? The concession expires soon they have to decide if to renew it, but they've taken all the coal out of the ground. But they think, maybe there is something else here. You know shale gas?'

'What's that?'

'Natural gas trapped in rocks, like you use for cooking or whatever. But the rocks are impermeable, so you have to break them open to let the gas out. You pump water and chemicals deep into the rock to make a fissure. Hydraulic fracturing. Sometimes it goes wrong.'

'Talhouett have been doing that here?'

'Very secret. Very illegal. They do not have a permit, but they want to know if there is gas before they renew the concession. But they make a mistake. They drill too deep, they disturb something. Suddenly, the water vanishes.'

'Exposing the church,' said Ellie. 'So when Saint-Lazare started sniffing around Talhouett, the Brotherhood got worried he knew about it.'

'So what's in here that's so valuable?' said Doug.

Ellie looked around the roofless church, the green sc.u.m on the walls, the effigies of the knights with their faces washed away. 'There must be something.'

Joost jerked the gun. Another bolt of fear flashed through Ellie.

'You think Talhouett have hid something here?'

'They're desperate to protect it,' Ellie said. 'But we don't know what it is. Something old.'

Joost considered this. His round eyes drifted to Doug's back. 'What's in the bag?'

'Something we took from the company.'

'Let me see.'

A prod from the gun gave them no choice. Doug unshouldered the bag and unzipped it to reveal the square cardboard box.

'What is it?'

Doug lifted out the cube. His breath fogged the glossy black surface.

'What the h.e.l.l is that?'

'I wish we knew,' said Ellie.

'Don't f.u.c.k with me, you people. It looks like a bomb.'

'We stole it from the company's vault. We don't know what it is. We think there might be a clue in this chapel.'

Joost's eyes bulged wide. 'You guys are crazier than me. If you're telling the truth. Maybe if we put a bullet in it something happens.'

He raised the rifle. Instinctively, Ellie moved to put herself between the gun and the box. Joost gave a manic laugh. 'So it's valuable.'

'To someone.' Ellie looked around, wondering desperately where Harry's friends might be.

'Give it to me.'

If she'd been braver, or watching the scene play out on TV, she might have wondered if he'd really shoot her. Standing in the cold, muddy chapel on the wrong end of a gun, her heart almost bursting out of her chest, she didn't doubt it. Even then, she hesitated. Joost squinted down the barrel of the rifle like an old-time gunfighter. She stood stock still, frozen like the stone knights on the floor.

Nye Stanton died trying to get it back.

She felt Doug's hand on her arm, tugging her away. She thought of her mother: her long, lonely years because her husband had thrown his life away. For what?

Swallowing her anguish, she closed the bag and slid it across the floor to Joost, who hooked it over his shoulder. She ached like a mother surrendering her child.

'So where do you find your clue?' Joost asked.

Concentrate. It helped take the pain away. She looked at the knights' effigies.

'They don't open,' Joost informed her. 'I tried. In case there was treasure inside, right?'

She felt dizzy. She leaned on one of the columns for balance. The ma.s.sy stone reminded her again of the Monsalvat vault.

Where's the most valuable place in a church?

Towards the back of the chapel, the mud floor sloped upwards. Ellie supposed there must be a dais underneath where the altar had once stood. She walked on to it and knelt. Damp seeped into her jeans. She dug her hands into the mud, feeling it ooze around her skin.

On her right middle finger, something shifted. Blanchard's ring she'd worn it so long now she'd forgotten she still had it on. She took her hand out of the mud, slid off the ring and shoved it in her pocket.

'Did you find something?' Doug asked.

She plunged her hand back in the mud. 'Not yet.'

Halfway down to her elbow, she felt something smooth and solid. She dug in with both hands, sc.r.a.ping like a dog. Doug joined her. Soon they'd excavated a small hole in the silt, down to the old church floor. Through the film of mud that caked the stones, she saw faint lines, like a diagram or a map.

'There's some sort of picture under here.'

They redoubled their efforts, scooping away mud to reveal the ghostly outline beneath. Eventually, they'd cleared a hole about a metre square. Joost brought a water bottle and splashed it over the stones. The tide carried away the last residue of mud, revealing the underlying mosaic as clear as the day it was laid.

They all stared. It looked like a knot, but with straight lines and sharply geometric corners that radiated out like the points of a star or a crown. There was a symmetry to it, almost mathematical, as if it plotted some unknown equation.

'It's a labyrinth,' said Doug. 'On mazy paths ... This must be it.'

'But it isn't a maze,' Ellie objected. 'There's no path. The lines criss-cross each other all over the place.'

She knelt in the mud and tried to sc.r.a.pe the edges of the mosaic clean. She took a nail file out of her bag and scratched at the stone, feeling for any sort of crack or lip she might lift.

A shadow fell over her. Joost held the camera pointed at the floor, his face screwed up as he stared at its screen.

'What are you doing?'

'Doc.u.menting the site. This is art, right? It's valuable.' Joost edged around to get a better angle. 'We're in France. If the politicians don't care that Talhouett f.u.c.ked the environment, maybe they care about the culture.'

Scratching it to pieces with a nail file isn't going to look too great on TV. Ignoring the camera, Ellie kept prying at the stones. They wouldn't budge. The mosaic tiles were almost seamless.

'Maybe there?' Still filming, Joost pointed to the middle of the design where the lines made a blocky cross. 'X marks the spot, right?'

But try as she might, she couldn't get them loose. She was concentrating so hard she didn't hear the throb of engines, not until Joost grabbed the collar of her coat and pulled her up. He dragged her to the gla.s.sless window. On the far side of the lake, a black 4x4 and two red pickup trucks jolted down a track between the trees.

'Did you bring them here?'

Ellie was trembling so hard she barely managed to speak. 'They want to kill us.'

The absolute terror in her voice dispelled any doubts Joost might have had. He let her go. On the far edge of the lakebed, the vehicles pulled up at the top of the slope. Half a dozen men jumped out: they surveyed the wasteland below, then began sliding down the embankment towards the mudflat.

'Are those guns they're carrying?'

'I told you, what they're doing here is very illegal.' Joost stuffed the camera into the backpack and slung the rifle over his shoulder. 'If they get caught, it costs hundreds of millions of euros. You think your life is worth more to them?'

'What about the mosaic?' Doug scrabbled on the floor, desperate. 'We haven't found anything yet.'

'You want to be around when they get here? Be my guest.'

Ellie peered out the window again. The guards were still stuck on the sh.o.r.e, tentatively testing the mud to see if it would hold them. They'd come down on the far side of the lake from the stepping stones: it would take them a while to work their way round.

'Is there another way to get here?'

'Not unless they have a helicopter.'

From somewhere unseen, a low tremor disturbed the air. It echoed around the bowl of the lake like gunfire. Ellie stared at Joost.

'I hope you were joking.'

A small helicopter in Talhouett colours swept over the ridge and touched down next to the cars. Two men clambered on to the skids.

'Now what?'

In the corner, Joost was fumbling something out of his bag. It looked like a pistol, though with an absurdly wide barrel, like something out of a cartoon. He tucked it into his waistband.

'Excuse me, but I think we should get the f.u.c.k out of here.' He ran to the walls and made a stirrup with his hands. 'Through the window. They see us if we go out the door.'

Doug took a last look at the mosaic. Ellie didn't wait. She put her foot in Joost's hands and let him lift her up to the sill. She squeezed through the narrow Norman window and dropped down on to the rock. Doug followed a moment later, pausing in the gap to help Joost after him.

The church blocked their view, but the sounds told their own story. Ellie could hear the pitch of the rotors rise as the machine lifted off; the whomp-whomp of the blades as it flew low over the lakebed towards them. It seemed impossible that she could outrun it, but she knew she had to try.

The stepping stones seemed further apart than before and more treacherous: each time she put a foot down, she thought it would skid out under her and pitch her into the mud. She looked back, to check that Joost was still with them.

Joost hadn't come. He was crouching behind the church wall, fiddling with his outsize pistol. Ellie hesitated. The helicopter noise was all around them now, almost on top of her. But Joost still had the backpack.

A wall of air hit her as the helicopter came up over the church. It almost knocked her flat on the ground. One of the men perched on the skids saw her and aimed his rifle. She put up her hands. I surrender.

But they hadn't seen Joost. Tight against the wall, almost directly below the hovering aircraft, he was invisible to them. The helicopter banked, looking for a place to set down. Joost stepped out from his cover.

A bright light whooshed out of his hands, straight into the helicopter. The c.o.c.kpit lit up like a supernova. Time seemed to slow down. The helicopter thrashed the air like a dying bird, then plunged to the earth.

Hypnotised by the dying aircraft, Ellie didn't see what hit her. All she felt was the impact the next thing she knew she was flat on her back. Wet mud sucked her in; it seeped up her back; it trickled in her ear. The ground shook. A bright light seared the sky and a crashing roar enveloped her. Hot breath blew against her.

Then Doug was over her, reaching down, putting an arm under her back and hauling her up. Joost was there too. Behind him, a pillar of flames and black smoke seethed out of the sh.e.l.l of the church. The Normans had built to last, but even they couldn't withstand that impact. The old walls, eroded by their long immersion, collapsed. The fire swallowed them, belching out the fragments it couldn't digest in a series of secondary explosions. A piece of rock the size of a fist flew past Ellie's head, inches wide. A smaller one grazed her face.

She crawled forward, bounding from stone to stone like an animal. Debris peppered her back. Shielding her face with her arm, she glanced over her shoulder. Through the smoke, she saw the men from the cars had come down to the sh.o.r.e. Light flashed from the muzzles of their guns.

'Don't s.h.i.t yourself!' Joost called. 'From this range, they're shooting wild!'

More shots came. Not far away, Ellie saw the bullets cutting plumes of mud out of the lakebed.

'Keep moving.'

They leaped off the final stone and staggered up the incline to the trees. Ellie's lungs ached; blood was pounding in her ears. She thought she heard a car up the hill to her right, but she carried on regardless. Joost's hand on her shoulder spun her round.

'Our car's that way!' she shouted.

'So are the bad guys.' Joost slipped off the backpack and gave it to Doug. 'This is too G.o.ddam heavy. I need my arms free for shooting, OK?'

'How are we getting out of here?' Ellie had been so fixated on crossing the lake, she'd forgotten about the fence.

But Joost was already heading through the trees. She followed blindly, hoping he knew where he was going. A car door slammed in the distance; a minute later a volley of sub-machine-gun fire ripped through the forest. Branches snapped; lumps of wood erupted from the dead trees.

Joost slid to the ground in a narrow defile, in the shadow of a fallen tree trunk. He aimed the rifle and squeezed off two shots. The gunfire stopped for a moment, then came back with renewed ferocity. Several bullets. .h.i.t the tree trunk, but didn't get through.

'I think there's only two of them,' Joost announced. 'You said you have a car?'

'We left it in the woods on the other side of the road.'

He jerked his head back. 'Two hundred metres that way, you find a tree with a red ribbon tied on it. Behind it there is a hole in the fence. Get your car: I meet you there. The camera's in the bag. If anything happens to me, you send those pictures to the Green Knights, OK? They know what to do.'