A dozen paces down the tunnel, there was an opening on the left. From it, Carver could hear the sound of rushing water, moving much faster than anything he’d heard so far. He stopped by the opening, flattening himself against the wall. He took a deep breath to calm his pulse, and placed his left hand holding the dazzler directly under his right hand holding the gun, so that each steadied the other. Then he stepped out into the open, feet apart, legs bent, arms straight out in front of him.

There was no one there. In front of Carver stretched another, much bigger tunnel. From the ceiling, placards and display cases were suspended in midair on steel wire, the whole history of the Paris sewers stretching away into the distance. Directly underneath all the displays, thick steel mesh covered a working, gushing sewer. That was where the noise of water was coming from. To the sides, along the walls of the tunnel, concrete walkways kept visitors firmly on dry land.

Carver stepped back into the cross tunnel and walked on. There was still water flowing all around him, but much more sluggishly now. And the smell was suddenly more intense, a nauseating stench of human waste.

Up ahead, a massive pipe hung from the ceiling, banded with striped warning tape to prevent people from banging their heads. Beyond it was another junction, where the tunnel split in two. The left-hand fork was a narrow tube of concrete; the right-hand one was wider, with a walkway running beside a sewer covered with a raised metal cage. Carver went left. There was no big strategic logic, he just figured the concrete tunnel would smell less rank.

Carver went on, shifting the dazzler beam forward and back, listening intently for any sound of human movement. He almost fell into the huge open space at the end of the tunnel, stopping himself just in time before he crashed onto the floor. He pulled back a couple of feet, wondering why there hadn’t yet been a shot. The hostiles must be close now. Why didn’t they fire? Had they gone down the other way without him noticing? Was he outflanked?

He shone the dazzler back the way he had come. No one there. He turned again, hands together, stepped out into the space, and… nothing, just a cavernous emptiness. He stepped forward a few more paces. The beam of the dazzler caught a vast black ball in its alcove and the splintered body of a half-open red wooden door, through which Carver could see stairs curving up to ground level. That was how his enemy had got in, but where the hell were they?

Carver stepped forward, stopped, then began a slow, deliberate rotation, sweeping the whole space with light, his gun following the dazzler all the way. He was halfway around when he heard a grunt behind him, a human sound, like a weightlifter struggling to shift a massive load. It was immediately followed by the creaking of wood under pressure. Carver spun around just as the massive spherical mass came free from its housing and started rolling toward him. He fired four shots straight at the giant black ball, but the bullets ricocheted off the wood, leaving barely a mark on the rock-hard surface, the reverberating gunfire mixing with the deep, hard rumble of the ball against the concrete.

He turned to run back toward the mouth of the narrow tunnel, just a few feet away, but slipped on a patch of water on the bare concrete floor and stumbled. The ball was almost on top of him. Desperately Carver scrabbled to his feet, dropping the dazzler, which was crushed beneath the ball like a tin can beneath a jackboot. The man-made cave was plunged into darkness, and Carver threw himself back into the tunnel. He heard the giant ball smash against the entrance, too big to penetrate any farther.

Frantically, he started running into the pitch-black void in front of him. He shifted his gun into his left hand and placed the fingers of his right hand against the wall to act as his guide. He was totally blind, but he forced himself to sprint flat out into nothingness, though every instinct screamed at him to go slowly.

He reckoned the tunnel was about twenty paces long. Then came the junction. The other guy would be coming that way. Carver listened. He could just hear one set of slow, steady, watchful footsteps – the steps of a man who wants to hunt down his enemy without becoming the prey himself.

Carver looked left and saw a faint flashlight beam emerging from the darkness. It was sweeping from side to side as the man behind it searched for him. He turned toward the opening of the other tunnel and fired three quick shots. He wasn’t expecting to score any hits, he just needed to force the other guy to take cover, even for a few seconds.

He could still make this work. He turned again, reached for the wall, and ran on into the blackness.

Kursk was on the offensive. He had forced his enemy to retreat and smashed his most important weapon. Without the dazzler to light up his target, the Englishman’s gun was far less of a threat. Now Kursk had to press home his advantage.

He had gone no more than five paces down the other tunnel, walking parallel to the one down which the Englishman had fled, when he saw the glint from a pistol barrel in the flashlight beam.

Kursk flung himself to the ground as three bullets ricocheted off the walls around him. The moment he hit the ground, he switched off the flashlight, making himself invisible again.

He heard the Englishman’s footsteps moving away from him, fast. Kursk turned the flashlight back on and kept going to the end of the tunnel. He saw the pipe with its striped tape, but beyond that, nothing. The Englishman must have turned off the passage somewhere, gone down another way.

Ahead on the right, Kursk could see the arch of another tunnel, from which came the sound of fast-moving water. He ran toward it, then, without stopping, flung himself to the floor, rolling across the open arch, firing into it as he went. As he reached the far side, two bullets smashed against the wall, showering him in dust and concrete chips. Well, that answered one question. The Englishman had found a new escape route.

As the echoes of gunfire faded away, Kursk thought he could hear something over the sound of water: a scuffling movement in the darkness, then a louder bang and a muffled curse. It was all he could do not to laugh. The poor bastard had bumped into something, trying to run away in the dark.

Okay, time to see where the Englishman was hiding. Kursk got to his feet, then sprinted back across the open archway, holding his gun away from him, so that anyone aiming at the flashlight would not hit him. This time, he looked down the tunnel, seeing the boards and display cases suspended between the ceiling and the metal-grate floor. Maybe the Englishman thought he could hide behind them. Well, he’d see about that.

He switched off the flashlight. Now they were both blind. He slipped to the floor and slid on his belly to the center of the archway. Then he moved forward until he could feel the surface beneath him change from concrete to metal. A blast of chill, damp, fetid air hit him from the sewage water racing beneath him. He reached forward and felt the first wire, as taut as the guy rope of a tent, holding a Plexiglas display case in place. Slowly, silently, he slithered underneath the case, making his way through the tangle of wire securing it to the floor.

When he came out the other side, into the gap between the cases, he paused, listening for any sound of the Englishman. Where had the bastard gone? Kursk darted his head from side to side, cocking his ear, suddenly nervous that the Englishman was nearby. The two men could be centimeters apart. With the darkness, and the noise and smell of the water, they’d never know it. He willed himself to wait, be patient. This was a matter of who lost their nerve and made the move that gave away their position.