Necropolis by Anthony Horowitz

if anyone actually lived there — or was it simply there for the Gatekeepers, its only inhabitants?
    At any event, he had gone back there almost every night, floating out of the bed, out of the room, out of himself. Then he had begun to travel, searching for Scar. Sometimes he would see a flicker of lightning, an approaching storm. Once, he found footprints. Another time he came upon a grove of trees, which at least proved that the place wasn't entirely dead, that things could grow there.
    But there had never been any sign of Scar.
    There was no point in searching for her tonight. In just twenty-four hours he would be meeting her anyway. But even so — maybe it was just habit — he found himself back in the dreamworld almost at once. As usual, he was on his own. He was climbing a steep hill, but it took no more effort than if he had been walking on level ground. Far behind him, the wilderness stretched out, wide and empty.
    And then he noticed something strange. The ground underneath his feet had changed. He knelt down and examined it, brushing aside the dust that covered everything. It was true. He was standing on a path fashioned out of paving stones that had been brought here and laid in place. He could see the joins, the cement gluing everything together. Even though he was asleep, Matt felt a surge of excitement. A man-made path! This was completely new and confirmed what he had always thought: The dreamworld was inhabited. There might be buildings, even whole cities there.
    He looked up. The path had to lead somewhere. There could be something on the other side of the hill.
    But he wasn't going to find out — not then. Suddenly he was awake. Someone was shaking him, calling his name. The lights were on in his room. He opened his eyes. It was Richard.
    "Wake up, Matt," he was saying. "There's someone here."
    EIGHT
    The Man from Lima
    Matt heaved himself out of bed, threw on some shorts and a T-shirt, and ran downstairs barefoot. The whole house was awake. There were lights on everywhere and the alarm system was buzzing, warning them that somebody was approaching.
    It had already occurred to him that this sudden interruption must be connected to the fact that Scarlett had been found. If all five of the Gatekeepers were now out there and known to each other, that made them a greater danger to the Old Ones, and it was no surprise that they'd want to take action. It was exactly what he and Richard had been worrying about. On the other hand, it could be a false alarm. Over the past four months, there had been plenty enough of those. Sometimes the children came out from the town, looking for food or something to steal. Professor Chambers kept llamas for their wool, and one of them might have broken loose. The system was sensitive. Even a bat or a large moth might have been enough to set it off.
    Matt hurried into the main room. There was a computer standing on a table in the corner and it had already activated itself, automatically connecting to the radar on the roof. It showed a single blip moving slowly and purposefully toward the front door. It was half past one. A bit late for a visitor.
    Jamie and Scott had come downstairs, fully dressed. Pedro followed them — barefoot like Matt, but then he often preferred to walk without shoes. He was yawning and pulling on a sweater. Joanna Chambers had arrived ahead of everyone. She was wearing an old dressing gown. Matt watched her open the gun cabinet and take out a rifle. So far, nobody had spoken.

    "What's happening?" Jamie asked.
    "A single figure moving through the garden." She nodded at the computer. "It looks like there's only one of them, but we can't be sure."
    Richard went over and examined the screen. "I'd say he's trying not to be seen," he muttered. "Why don't we take a look at him?"
    He leaned over and pressed a switch. This was another part of the security system. The entire garden was instantly lit up by a series of arc lamps so bright that it was as if he had