"Whose law?" Caird muttered.

His pursuers were organics, but they were also immers. There had not been time for them to go to a precinct station and withdraw charged-particle beam weapons. These two must have been in the neighborhood or close to it, and they must have been looking for him. They were lucky-unlucky for him-to be the nearest to Ruth Dinsdale when she had called in. They had brought out the illegal weapons, their own property, from a hidden place in the car, and they meant to use them.

Caird went down the ladder for thirty feet before stepping off onto the rubbery plastic walkway. It extended east and west as far as he could see, which was not more than a hundred feet either way. Whichever way he went, the lights would travel with him and darkness would follow and precede him.

The walkway was bounded on one side by a thick plastic wall and on the other by a guardrail. Beyond it were two goods transportation belts, each fifteen feet wide. At the moment, they were not moving. Beyond them, against the wall, were two huge pipes. One was a water main; the other was for sewage.

Because he was both an organic and an immer, Caird had studied the systems. Every three hundred feet the rock wall bore tunnel and belt identification signs and diagrams of the local system. By each was a communication strip. These could also be used to monitor the tunnel. If the men after him took time to call in to an immer at the monitor control center, they could check with the monitor through the tunnel strips. The monitor could tell them exactly where their quarry was.

He did not know if the immers had anybody at the control center. He could not take the chance they might not have one. He had to get to a place where there were no monitors. Though he knew of such a place and was running toward it, he would encounter dangers there of which his pursuers would be only one.

He ran, his feet slapping the walk and his breathing the only sounds. When he looked back, he saw another light following him. The two men were tiny figures inside a worm of light. They were about six hundred feet behind him, too far for effective range of their guns. He had to keep that distance. So far, they had not stopped to call in and they would have if they had someone at the monitor control center.

The tunnel sloped down so gradually that he would not have been aware of it if he had not studied the system. It would pass under the Kropotkin Canal, but, before it got there, he would come to two tunnels crossing this tunnel at right angles. He took the first one and ran north. The belt by the walkway was lower than the previous one and was carrying a few boxes of goods. The belt plates, two microns thick, were not joined but moved silently like a caravan of caterpillars, one behind the other. They slid on the lubricant provided by the continuous strip beneath them and were propelled by magnetic impulses.

Jogging, looking back often to make sure that his pursuers had not broken into a run, Caird kept on until he came to a three-level tunnel intersection. Just off the walkway was a large room cut out of the dirt, rocks, and cement blocks forming the first level under the streets of Manhattan. The room was walled, floored, and ceilinged with thick plastic. He went into it, the lights turning on as he entered. This was a tool and recreation room and toilet for the workers. After looking hurriedly around, he ran to a table and picked up a flashlight, two batteries, a hammer, and a screwdriver with a long thin shaft. He tested the flashlight and put the five artifacts in his shoulderbag. On the way out, he stopped to drink from a fountain.

Coming out of the room, he saw that the two had gained on him. One raised his weapon and fired. Caird ducked even though the movement was useless. The ray struck close to him but did not damage the wall. He jogged faster than before. The two were gaining on him at the rate of about ten feet every ten seconds. He increased his speed so that he could get to the previous six-hundred-foot distance from them.

Beginning to pant now, he ran toward his first goal, a yellow enclosure of uprights circled by two horizontal rails. He was running so fast that he had to stop himself by grabbing the top railing. He went around it and let himself swiftly down another plastic ladder. Just as his head disappeared into the hole, the light above him went out. An angry yell reached him before he was halfway down the ladder.

"You won't go so fast now, you bastards," he muttered. At the foot of the ladder, he groped in the bag and brought out the flashlight. Its ray, poking here and there, showed him what was left of the old transportation belts. This system had been aban doned seven hundred obyears ago when the second great earthquake had struck Manhattan. The plates were thick aluminum alloy, many of them torn off or buckled. The gaps exposed the rusty and dislodged rollers beneath. The system had been obsolete long before it, along with three-fourths of the buildings on the island, had been destroyed by the temblor.

That catastrophe had been terrible, though not as difficult to recover from as the even greater quake of N.E. 498. On this level, however, the quick-drying plastic sprayed thickly to enclose the tunnels had not been as twisted as that on the first level. It was bad enough. Here and there, the plastic had been bent out past its strength to withstand the shock. Dirt had spilled through the cracks, and seepage had brought more dirt through. The flashlight showed no complete blockage trapping him. Not in this area.

The light had come on above him. The two were getting closer. He hesitated. He could get away as fast as possible from here or he could wait and try to knock out or kill the first one to come down the ladder. To do that, he would have to retreat beyond the range of their flashlights while they played the beams from the entrance above. Then he must run in after the first man began the descent, and somehow ... No. If he threw the hammer, it might miss or only slightly hurt the immer. Both men would have their guns in their hands, and the one above would be directing his flashlight into the area below.

Just as he decided not to attack, the expected light beam came down through the entrance hole past the ladder. Caird turned and walked swiftly away, hoping that he was going in the right direction for him. There was enough light from the hole for him to see dimly for some distance ahead of him, though he had rough footing. The walkway was buckled and bent, and once he almost stepped into a gap.

Knowing that the man to first come down would stop on the ladder and explore the area with his light, Caird stepped up his pace. He did look back once. Seeing the beam dart around, he got down behind a pile of wet dirt that had fallen through a hole in the wall. He was just in time. The light played on the mound and then went away.

Caird's second goal, if he remembered correctly, was about four hundred feet away. He got up and stumbled on, feeling his way by the walkway railing, walking crouched over, afraid that he would fall. And then he did tumble, sprawling forward when he stepped onto a part of the walkway that was not there. He repressed a shout and shot his arms out and across to avoid injury if he struck something. He landed unhurt in a small hole. He did not get up at once because the beam shot above him. If he had been upright, he would have been caught in it.

The tunnel amplified sounds. He heard one of the men say, in a low tone, "Where'd he go so fast? We shouldn't split up!"

"You're talking too ... " the other man said. His voice died down so that Caird could hear only a muttering.

"Too loud," Caird finished for him. They would probably stay together and explore the areas in both directions for a hundred or so yards. Watching from the edge of the broken walkway, he saw them turn away from him. He breathed easier. He crawled back onto the runway and continued on hands and knees. When a beam flashed near him, he flattened out. They would be turning from time to time to try to catch him with the beam.