The man-apes of Africa were perpetually starving, the victims of drought and lack of food. At dawn, Moon-Watcher noticed that his father had died, took the corpse out of the cave and continued about his business. Later he foraged for berries and other edible plants with two of his compatriots from other caves. Moon-Watch was one of the largest of his group and the only one able to walk upright. The tribe often went without food. As they gathered berries, the man-apes were unaware of the potential source of nourishment in the antelope- like creatures that ate beside them.

Moon-Watcher awoke late that night, to the sound of a large beast dragging a carcass. Then, he heard an unidentifiable sound, that had never before existed in the world—metal clanging against stone. As Moon-Watcher's tribe headed to the river, he first encountered the New Rock. After glaring at it, Moon- Watcher licked it, discovered it was of no nutritional value, and continued on. As the tribe approached the Rock on its way back from an unsuccessful day of foraging, a foreign sound, a repetitive vibration, began. As the sound increased in volume, the man-apes were drawn closer to the Rock; they stood in front of it, totally hypnotized. Unknown to the man-apes, their minds were being studied, their bodies probed, and their actions controlled.

One entranced man-ape picked up a piece of grass, tried and failed to tie a knot. Then another man-ape tried and another, until a young man-ape tied the first knot ever on Earth. When Moon-Watcher was possessed, he picked up stones, trying to throw them at a bulls-eye on the monolith. An intense pleasure overcame him when, after many attempts, he finally succeeded.

As the days went on, the monolith ignored most of the man-apes, but continued to interact with some of them, including Moon-Watcher. His mind was being developed, even though his instincts made him want to break free of the monolith. One day as a group of pigs came across his tribe, Moon-Watcher experienced an entirely new set of impulses. He looked around for a rock, picked it up and ran toward a pig, and killed it. The man-apes learned to feast on the dead pig—their hunger problem was solved.

The man-apes were taught to use many other tools and soon enough the tools became a part of their everyday lives. With near-starvation no longer a pressing concern, the man-apes first experience leisure and the evolutionary predecessor of thought. One day, Moon-Watcher's tribe came across a dead animal. As dusk was nearing, it was not safe for the man-apes to be out with the carcass. It dawned on Moon-Watch that he could drag the animal back to his cave. He began to do so, sometimes aided, sometimes hindered by the other members of his tribe, who could barely understand what he was doing.

Still, a giant and fearful leopard haunted the tribe. One evening, in came into Moon-Watcher's cave. He began to attack it with some of the tools they had developed for hunting. His fellow tribesman joined in and the leopard ran from the cave, disappearing over a precipice, and plunging to its death. The tribe found the dead leopard the following day. They cut off the head and carried it about with them. They displayed this to a rival tribe, which cowered in fear. Moon-Watcher began to understand that he need no longer feared the leopard, "now he was master of his world."