Everything was ordinary. Men worked in factories and fields. Women were shopping. Children were at school. Then came the four-minute warning. Wires hummed madly between heads of governments. Just before the massive retaliation went into the air the world realised that no-one had despatched the first rocket. The retaliation was checked with seconds to spare. Experts examined the ruined city. There was something else besides radiation. Deadly bacteria from an unknown source spread across the planet. More alien bombs followed the first. But there was no real pattern to the attacks, if they were genuine attacks.

At last the detectors found the alien ships. They were fighting among themselves and earth was the battle-area. Could the remnants of humanity interfere? What would be the result if they did?

Humanity played with fire once too often. It was atomic fire and its ravages produced an almost complete annihilation, but there were survivors. The radiations had not been entirely malevolent in their influence. Genes and chromosomes danced like dervishes in the gamma bombardments, and settled back into fantastic new patterns. God-like beings strode proudly athwart the devastation. Half-human demons lurked in the shadowy ruins. The twilight of humanity faded into a new heroic epoch, behind which the forbidden secrets of the ancient atom gods bided their time...

Nathkrul had to make an agonising decision. Dare he risk using the forbidden weapons or - must he let the Dark Ones win?

Man is an intelligent mammal. His intelligence lies in his brain. In mammals the tissues of the central nervous system are irreplaceable. The brain contains somethine like 100,000,000,000,000 neurons, but 100,000 are destroyed on an average each day of a man's life. Cosmic rays and general internal and external radioactivity account for most of this destruction.

Hunter and Gradey decided on an illegal experiment. They brought up a small group of children in a strange artificial setting where there was practically no radiation. The setting was improved. The environment grew more shielded as generations passed. At last the Thinkers exploded into a world that had not dreamt of their existence. The world was facing other complications at that moment. An alien had appeared from the other side of the cosmos! Humanity was faced with two potentially deadly enemies; could they be turned against each other, or was one a secret friend?