Corax, an escaped slave, flees Rome on the first ship in port. He lands at Caesarea, the city from which Pontius Pilate governs the province of Palestine. His goal is the source of the sacred Ganges River whose purifying waters flow through the country of his father's birth. To earn money for the journey he works in the marketplace as a healer using skills acquired from his father and in the household of his former master, Cornelius Celsus, a patrician collector of medical lore.

Twice he encounters a burly Essene, the rebel Jeshua, before the Romans identify Corax as a runaway and imprison him. About to be branded and enslaved once more, Corax buys his freedom by betraying a secret: the hour when the bandit Bar Abbas will attack Pilate's fortress to free the prisoners there. But it is Jeshua - Jesus - who is accused of the betrayal so he, too, must flee Palestine.

The two, the guilty and the unjustly accused, make the perilous journey east together. They cross the chaotic remnants of Alexander's empire, eluding violent Scythians and Huns, encountering Zoroastrian magi and Buddhist sages. And when they reach the foothills of the Himalayas, Jesus receives the life-altering revelation that will change the world.