Destroyed by self-repairing machines arriving from outer space, the Earth perished at the end of the Age of the Forge of God. Several thousand people were nevertheless saved by robots sent by the Benefactors to protect primitive worlds and civilizations from devastation. The robots successfully dealt with planet-killing probes throughout the solar system, but the Earth, nevertheless, was completely destroyed. While conditions for life were being created on Mars, the rescued people were on board the huge Central Ark. Here they were introduced to the Law - the galactic code that determined the behavior of civilizations. The law stated that civilizations that created self-repairing killing machines must be destroyed. Now people, with the help of the Benefactors, had to administer Justice. The youngest inhabitants of the Central Ark volunteered to go on a long journey to maintain balance in the Galaxy.