Casca decides to leave the hold and set sail across the seas in two new longships that have been built and eighty young men volunteer to accompany him on what they see as a saga. Saying farewell to Glam they set out and after a few weeks at sea and enduring a storm, they sight land and repair their ships. Sailing down an almost endless shoreline they eventually camp ashore near a forest, and on a walk Casca is captured by strange tribesmen dressed in the likeness of Jaguars. Glam's son Olaf vows to remain with the ships until Casca 'the Walker' returns. Casca is taken to a great city far into the interior, Teotihuacan, capital of the Teotec people, and is sentenced to sacrifice on their altars. During the period leading to this he becomes intimate with a Teotec woman, Metah, and learns the Teotec tongue.
He instructs the high priest that sacrifices must stop but the priest ignores him and prepares him for the Day. Casca wears a jade mask carved into his likeness and walks to the top of the pyramid where his heart is cut out, but because of his immortality he reclaims it from a stunned priest and walks back down to ground level. Although he passes out once he is back in his quarters he has become, in the peoples' eyes, a god.
He gains control of the nation and stops sacrifices, much to the anger of the priest of the Jaguar sect who, to restore the old ways, invites the neighboring tribe of the Olmecs to invade and conquer the Teotec lands. When the two nations meet, the battle is decided by the use of Casca's Vikings who have been summoned from their ships by Casca. Casca himself kills the Olmec king in single combat but after the battle he learns the Jaguar priest has kidnapped Metah and is intending to sacrifice her. He chases the fugitive priest and comes across a badly wounded Metah who has been knifed by the priest. Returning to the city with Metah he learns she will die unless she is given fresh blood, so in an attempt to make her immortal he offers his blood. However his blood is poison and the transfusion kills Metah, plunging Casca into guilt-ridden grief.
He decides to leave the lands of Teotah and return to the lands he knows together with the surviving Vikings, after extracting from the people that sacrifices will stop, and placing his mask of jade in the hall reserved for that purpose.