Is human existence doomed to failure? Does man repeat the same mistakes again and again? Are humans incapable of learning from their past? Is continuous existence secured only in symbiosis with more highly developed life forms?
Jack Schilt is confronted with these questions when he finds himself sharing his body with a Sentry, a highly evolved species, on Gondwana in the year 622. But how and when did the alien creature find access into him? And why is it making itself felt now?
Jack sets out on an adventurous journey of discovery to search for his missing brother, who vanishes after they uncover life-changing artifacts contradicting the world as they know it. This journey leads him across forbidden lands and into mythical dangers as his knowledge about his true origins is shaken and reformed.