The first underground sewer was dug beneath the streets of Paris in 1370. Now there were 1,300 miles of tunnels beneath the city, known as les egouts. They carried away 1.2 million cubic meters of water and waste a day, and they directly followed the lines of the roads up above. Every tunnel was signposted with the name of the avenue, boulevard, street, or square whose filth it removed.

If you wanted to have a gun battle right in the middle of a major city, without anyone noticing, the sewers were the place to have it. But Paris went one better. It didn’t just have sewers, it had a sewer museum, a concrete-and-steel warren of tunnels and chambers, right underneath the south end of the Alma Bridge.

Carver scuttled down the narrow stairs, bare concrete walls on either side. At the bottom, the passage turned a sharp left. In front of him was a solid steel door. On it was a white sign with a red banner across it announcing Danger. Below the sign a padlock held a massive bolt in place.

He put a bullet through the padlock, blowing it open, then pushed against the door, which swung away from him into a pitch-black void filled with chill, damp air that smelled of drains. He turned on his dazzler, twisting the end to widen the beam, filling the black void with a ghostly, radioactive green glow. Ahead, the passage seemed to open up into a low, broad chamber. There was another lock on the inside of the door, operated by a metal wheel. Carver closed the door and turned the wheel. There wasn’t much chance the guys who were after him would come in that way. Only an idiot would charge down a narrow, dark corridor toward a man known to have a dazzler and almost certainly a gun as well. They’d find another way in. Even so, it never hurt to cover your back.

Carver walked on into the sewers, his torch in his left hand, the SIG-Sauer in his right, trying to work out the direction from which his enemy’s attack would come.

The first chamber consisted of two old sewer tunnels that ran side by side. The sewer was filled in with concrete to make a flat floor. The wall between the tunnels had been punctured by a series of low, egg-shaped arches to make a single space. Carver walked through one of the arches, then hurled himself to the ground, bringing his gun to bear as he rolled across the concrete. To his left, in the shadows on the edge of the green dazzler light, he’d seen a group of figures in boiler suits and miners’ helmets. It took him half a second to realize they were waxworks, part of the museum’s exhibition.

He got up sheepishly and dusted himself off. To his right there was another, smaller tunnel. A notice: “This Way for the Tour.” Carver followed it and went deeper into the tunnel.

Grigori Kursk had reached the far end of the Alma Bridge a few seconds after Carver. He’d tracked the Englishman right up to the point where he’d pulled that crazy stunt in front of the oncoming bus. By the time the bus had moved out of the way, he’d lost him.

For a second he thought the man had got away. Then, across the far side of the road, he saw Carver’s bike abandoned next to the kiosk. He drove the Ducati onto the sidewalk at the end of the bridge, parking it next to a waist-high metal cage that stood over an open manhole. Beneath the cage a metal spiral staircase descended into the ground.

Kursk gestured to his partner to approach the Englishman’s abandoned bike from the right. He moved left. The two of them dashed across the bridge. Kursk ran around the front of the stranded bus, while his partner darted between the bus and the cars piling up behind. As they approached the bike, they saw no sign of its rider. Then Kursk noticed the open gate and the concrete stairway behind it.

He stared at the signs on the kiosk, trying to work out what they meant from the mass of different languages and symbols. Okay, so this was some sort of visitors’ entrance to something. Which meant somewhere there had to be an exit, or maybe a fire escape. Which would need a manhole. Beneath his helmet, Kursk grinned. Now he knew how to beat the Englishman.

He told his partner what to do. Then he jogged back across the bridge to where his bike was parked against the metal cage. The top of the cage was hinged in the middle. One half opened up to allow access to the manhole underneath, and it was held in place with a padlock and chain.

Kursk took off his helmet, reached into the bike’s top box, and pulled out a tool kit in a black, roll-up nylon pouch. From this he removed a small pair of bolt-cutters, casually leaned over the cage, and cut the links of the chain. He lifted the hinged lid of the cage, stepped over the side railings, and started walking down the metal stairs. Once he was below ground, he reached into his jacket and took out his gun before clipping a small black flashlight onto a mount on top of the barrel.

At the bottom of the shaft, there was a double door that shone scarlet in the beam of the flashlight. It was an emergency exit, opening out, toward him. Kursk fired a three-bullet burst into the locking mechanism.

The sound of the gunfire reverberated into the darkness. The Englishman was bound to hear, but that was good. Kursk did not want to waste time wandering around the sewers of Paris, playing blindman’s bluff. He’d much rather draw his opponent on, tempting him into an ambush. But he still had to find a way of setting up that ambush.

He pulled open the splintered door, walked a few paces forward, and entered a sort of man-made cave, maybe fifty feet square and twelve to fifteen feet high. He could hear the sound of rushing water somewhere beneath him. The flashlight tracked across the concrete floor until it came to an inset metal grille, running the full width of the cave, maybe six feet across. A thick brown soup of sewage and drain water was running beneath it, filling the air with a heavy fecal smell. And people actually paid to come down here?

Kursk looked around for cover. The huge space was almost entirely bare. The only means of access to the cave were two tunnels, one narrow and floored with concrete, the other broader, with another grille floor, directly over the open sewer. They turned to the left, a few feet apart.

On the right was an alcove. Its far wall had a huge circle cut into it, maybe ten feet in diameter. In the middle of the circle, held on a low wooden frame, was a gigantic black sphere, like a huge cannonball, so high that Kursk could not reach its top. There was a scale model of the ball down on the floor, demonstrating that it was made of wooden planks, with a hollow core. An illustrated notice showed how the ball had once been used as a cleaning device, dragged through the main sewers, bashing against the sides and knocking the crud from the walls. Kursk scanned the notice. He examined the ball and the way it was held on its frame. Now he had a new plan.

Carver had heard the muffled echo of gunfire in front of him, somewhere in the distance, just as he emerged from a low, narrow tunnel into an underground plaza. He swept his dazzler around and tried to get his bearings. It looked like some kind of a junction, where a warren of underground routes converged at a single point. On all sides there were arches beyond which he could see nothing but the blackness of passageways disappearing into the depths. But the only tunnel that interested Carver opened directly ahead of where he was standing. He was sure the gunfire had come from its far end.

He moved forward, accepting the implied invitation. Whoever had fired those shots had wanted them to be heard. Carver understood completely: He wanted to get this over and done with too. There was something almost reassuring about the absolute nature of the game they were playing. All the whys and wherefores could be forgotten. He just had to kill the other guy before the other guy killed him. It was a simple, straightforward task. He liked that.