Atti is a Roman teenager with brains but very little brawn. When one of his schemes falls foul of Emperor Nero, Atti is forced to join the army and is sent to miserable, cold, wet Britannia where the natives are revolting - quite literally.

Things go from bad to worse when Atti is captured by Orla, a feisty teenage Celt and he uses his Roman smarts to help save her grandmother. Meanwhile a furious Nero has ordered more troops to crush the rebellion, led by Boudicca, warrior Queen of the Iceni tribe. Atti rejoins his fellow Romans and as the armies prepare for an historic showdown at the Battle of Watling Street, the two new friends find themselves on opposite sides of the battlefield.