A Princess of Mars, John Carter was unwillingly transported back to Earth. The story proper begins with his arrival back on Barsoom (Mars) after a ten-year separation with Dejah Thoris, their unborn child, and the Red Martian people of the nation of Helium, whom he has adopted as his own. Unfortunately, Carter materializes in the one place on Barsoom from which nobody is allowed to depart: the Valley Dor, which is the Barsoomian afterlife.After John Carter's arrival, a boat of Green Martians on the River Iss are ambushed by the previously unknown Plant Men. The lone survivor is his friend Tars Tarkas, the Jeddak of Thark, who has taken the pilgrimage to the Valley Dor to find Carter. Having saved their own lives, Carter and Tars Tarkas discover that the Therns, a white-skinned race of self-proclaimed gods, have for eons deceived the Barsoomians elsewhere with the lie that the pilgrimage to the Valley Dor is a journey to paradise. Most arrivals are killed by the beasts who dwell here, and the survivors enslaved or eaten by Therns.