The Spin, an ancient artificial cluster of eighty-eight planets and twenty-two suns - is in decline. The boundaries of the formerly prosperous Inside have shrunk to a mere eleven planets, their trade routes are cut off, and their last remaining source of income comes from selling the services of their vast industrial slave-colony - The Hive.
Then a group of Hivers escape. Led by Seldyan, they steal the last remaining legacy battleship, reverse the trance that has been imposed on it for eight thousand years, and leave the Inside behind. Their destination: the free colony of Web City. However when they arrive they realise all is not well - a new green star has appeared in the sky, sparking the growth of a socially repressive cult which is quickly taking over, making Seldyan wonder if Web City is any improvement on the Hive.
At the same time Harbour Master Hevalansa Vess, stripped of his role after the loss of the last ship, has his identity changed and is sent under cover in to the Hive to find out how Seldyan escaped. Wired into the living AI called the Mind Stack, he is forced to confront both his own past, and the institutionalised cruelty of the hierarchy he has been part of.
While Seldyan and her crew try to discover what has caused the new green star, Vess must choose between loyalty to the system that has nurtured and promoted him, and his sympathy for the mass of people it treats as slaves. He must also work out how far he trusts Vut, the gestalt insect entity that increasingly represents his contact with the Inside.
Meanwhile, the ancient ship, now with full access to its memories, has worked out the meaning of the green star for itself - and the existential threat to the Spin that it has been concealing for ten thousand years...