He trudged back up the stairs counting them mechanically, and was in the outer air again. The change from semi-darkness to light brought his multiple eyelids winking shut, screening his sight. He squinted toward the southern horizon, seeing nothing but wastes. What was that? From the tail of his eye he thought he saw a flash of light far out toward the west, but although he gazed at the spot for several minutes, it did not repeat. Dismissing it as a result of the glare, he stopped and entered the valve-house, which stood in the shadow of the towering reservoir. He finished his useless routine, touching gently the same things and looking in the same places as every day, and came outside. This time it was unmistakable. Something flashed in the sunlight out in the desert to the west, a piece of polished metal or glass. Or a weapon. Somebody was on the desert! He was immediately prompted to run atop the knoll, whistle and wave his tentacles so that they would not miss him, but some primal caution held him back until reason took hold of his chaotic mind. Out there was either a friend or an enemy. If it were a friend, it could only be his relief, and he wasn't due for another three years. Besides, he would be coming from the south. Therefore it was an enemy, some members of another colony coming to raid the water station! Bending low, he raced up the hill and threw himself into the central hollow, facing west. He drew from its holster the flash gun, which had killed the _odlat_, and cradled it beside him. His eyes strained on their stalks across the western wastes, ready for the first hint of suspicious movement. Intra-mural war had again broken out on Mars! It disturbed Peetn to have the first responsibility fall on him, but recollecting the tales that the oldsters used to tell him, he was a little proud too. The little band of water-station defenders had been heroes in those days of the past, not useless, forgotten automatons. There had been a real and vital reason for their bitter existence in the north. Peetn's presence, up till now, had been a formality. For a long time he lay sweeping the desert before him, waiting for another glimpse of his attackers, until suddenly he realized that another night was near. The sky had already begun to edge toward the dark end of the spectrum, and the light was lessening visibly. Peetn grew uneasy as the shadow of the box-like reservoir left its source and began a sinister march to the horizon behind him. The rising nightwind send cold _odlat_-tongues up and down his spindly back, and although he knew that no living thing could stand on the open desert during a Martian night, the coming of darkness brought fear rather than a sense of security. * * * * *