The Chronicles of Jonathon Postlethwaite: The Seed of Corruption by David S Denny

Towers of the Tallmen beyond the Upper City, in a great stagnant cloud that hung over the Tallmens’ abode.
     
                                Turning away from the Halls, Jonathon scrambled to the top of the roof above the Whisperer's home and was staggered at the view which greeted him. The roof dropped straight down into the street below, so far was the drop that he could barely make out the crowds whose voices drifted up to him.
                                Gasping and slightly dizzy, Jonathon crept back from the edge of the roof and looked up. Vast expanses of roof tops were visible from here too. Stretching out for miles upon miles the multi-tiered slums and hovels of the Lower City grew upwards, literally a few more feet each day as new living space was needed, towards the glowing Field Wall which was Dubh’s sky.
    In some places groups of buildings, like the one upon which he stood, surged upwards like hills above a plain of blackened tile, brick and concrete. A world of metropolitan hills and valleys, buttes and mesas, had evolved out of the undulating mass of brick, tile, concrete and steel.
    Jonathon knew that Dubh had many levels beneath the ground, but thought that they stopped at the surface, but it was evident that it did not. It continued upwards, each new level or building precariously perched on the previous one, overhanging the network of gorge- like streets as if they might suddenly plunge down on the milling hordes below; and they often did.
                                Sitting on the mossy tiles above the Whisperer’s abode, Jonathon felt relaxed and safe. It was so different from life in his Grandfather's subterranean refuge where terror and fear had always surrounded them.
    Here it was almost beautiful, enveloped as he was by the calmness of this roof top world way above the masses below and under the soothing openness of the pseudo sky. But Jonathon would not relax; he had learned that lesson with his recent experiences on the street. He closed his eyes and stretched his consciousness out across the roof tops, searching for the minds of those who might do him harm.
                                He quickly established that the Whisperers were not the only inhabitants of this roof top world, other small groups and individuals lived amongst the mossy tiles and the damp concrete.
                                Jonathon detected the presence of huddled forms sleeping or idling, waiting for the onset of night when they would descend into the pits of darkness below to seek out a living. They were thieves, pickpockets - scavengers who found refuge on the roofs here from the Tans. Many were as spiritually sick as the mass of the population below, yet many unconsciously had sought a sanctuary from the forces which preyed upon their human kin on the crowded streets of Dubh.They were not suited to the world which ebbed and flowed with corruption and so sought a refuge and found it in the sea of calm which enveloped the highest points of Dubh most of the time.
                                The rooftops seemed a safer alternative to the street. Even the dark souls his mind  had  touched here  were  strangely  restrained.   For   reasons   he could not fathom, Dubh's spirit of corruption could not motivate them as it did others below, could  not physically reach them here. Or perhaps they were just not worth its effort.
    Just as Jonathon was about to return to the shack, he spotted two figures moving rapidly in the distance on a route that would bring them right upon him.
                                At this distance they were merely dark specks, yet moved at an incredible pace. These individuals did not move  around  in  the  tentative  manner  he  had  done   to reach this vantage point, they ran and bounded across