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 in 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?