Roman Britain, 208 AD: the Emperor Septimus Severus has arrived in Britain, intending to conquer the troublesome barbarians in the north once and for all. To Memnon, an African scout serving with a cavalry unit, the expedition seems at first just a continuation of his army life. On a journey north, however, he saves the lives of a senior member of the Emperor's staff and a beautiful young attendant of the Empress. Through them he becomes aware of a ruthless struggle for power within the imperial house. The bitter war will test all of them to the limit, and if they are to survive, it can ony be through their friendship - and belief in the Empire.