Set in 130 A.D. on Hadrian's Wall just as work on the wall is nearing completion. Two boys, Marcus and Telemachus, join their father, a Roman commander, in one of the forts. Marcus soon makes friends with a local boy, Bran, whose family are Brigantes but friendly towards the occupying Romans. Bran's sister Rhiannon hates the Romans but Telemachus is attracted to her and they begin to fall in love. Marcus, exploring outside the Roman enclave, is kidnapped along with Bran and Rhiannan. Telemachus helps to rescue them and in the course of this adventure, meets the spirit of the old Queen of the Brigantes, Cartimandua, who saw the benefits of working with the Romans.