Childhood's End is a 1953 science fiction novel by Arthur C. Clarke about a peaceful alien invasion of Earth by the mysterious Overlords, whose arrival begins decades of apparent utopia under indirect alien rule, at the cost of human identity and culture.
In the late 20th century, vast alien spaceships suddenly position themselves above Earth's principal cities. The aliens announce they are assuming supervision of international affairs to prevent humanity's extinction. The Overlord Karellen, the "Supervisor for Earth," reveals that the Overlords will reveal themselves in 50 years, when humanity will have become used to their presence. Humankind enters a golden age of prosperity at the expense of creativity. Five decades after their arrival, the Overlords reveal their appearance, resembling demons. This was later revealed to be a racial premonition of the Overlords' role in their metamorphosis.
Over a century after the Overlords' arrival, human children begin to display clairvoyance and telekinetic powers. Karellen reveals that the Overlords' purpose is to serve the Overmind, a vast cosmic intelligence, born of merged ancient civilizations and freed from the limitations of material existence. The Overlords themselves are unable to join the Overmind and serve instead as a bridge to join other species to the Overmind. The children's minds reach into each other and merge into a single vast group consciousness, completely alien to the original human. They are segregated on a continent of their own and no more human children are born.
Eighty years later, Jan Rodricks emerges from hibernation on the Overlord supply ship and returns to an altered Earth. Humanity has effectively become extinct and he is now the last man alive. Hundreds of millions of children have become a single intelligence ready to join the Overmind. The Overlords leave and Rodricks chooses to stay to witness Earth's end. Rodricks sees a vast burning column ascending from the planet and senses a profound sense of emptiness when the children have gone. The Earth itself then begins to dissolve and evaporates in a flash of light, marking the end of the human species.