The Liberator's encounter with the alien fleet has left if severely damaged and the crew must abandon ship. It is now a fight for survival and Avon and Vila struggle to discern friend from enemy amongst the chaos. The crew's only hope seems to lie on the allied planet of Obisidian which offers the prospect of safety and protection. However, Obsidian hides a deadly secret of its own. With the new crew scattered throught the Universe, they try to return to their ailing ship, now in the hands of Federation survivors, but still controlled by the talking computer Zen who will only take orders from the original crew.