Twelve-year-old Stephanie Harrington, a genetically-enhanced girl on the pioneer planet of Sphinx, bonds with a treecat, a telepathic and fully sentient animal, putting her in danger from highly placed enemies who want to ensure that the planet remains entirely in human hands.

In the year of grace 1345, as Sir Roger Baron de Tourneville is gathering an army to join King Edward III in the war against France, a most astonishing event occurs: a huge silver ship descends through the sky and lands in a pasture beside the little village of Ansby in northeastern Lincolnshire. The Wersgorix, whose scouting ship it is, are quite expert at taking over planets, and having determined from orbit that this one was suitable, they initiate...