Menace from the Past - E. C. Tubb - Bog

The alleys of Turgan were thin fingers of twisting darkness, writhing in an intricate pattern as they wended between the high walls of ancient houses. Old were these houses, old with the slow passage of a hundred thousand years, and they stared down at the sand-filled alleys with blank faces and the blind eyes of barred doors.
Even in daylight it was hard to find a man in the maze of the old town, at night it was impossible and Fenris was glad of it.
He tensed, crouching down beside a wall smoothed to a dull polish by the whispering sand storms of Mars, and strained his ears at a subtle sound. It came again, a soft scuff of sandled feet against the dust, the harsh sound of indrawn breath, and the faint click of metal against metal as weapons touched buckles or rasped against stone.
High above, the twin moons cast a faint light, a ghostly luminescence, vague and insubstantial, like the dream-glow of the Dryland Shamans and their magic globes of a long-dead science . . .