Esca is a proud Briton who has been enslaved by the Roman Empire. His hatred for all things Roman is challenged when Marcus impulsively gets his young life spared at a gladiatorial contest. Vowing to serve the man who saved his life, Esca accompanies Marcus in search of the Eagle of the Ninth. However, when they encounter an ex-Roman soldier, Marcus realizes that the mystery of his father’s disappearance may well be linked to the secret of his own slave’s identity and loyalty – a secret all the more pressing when the two come face-to-face with the warriors of the fearsome Seal Prince.