City of Skulls!

Dejah Thoris and Sola travel through the Martian desert to engage in the civil affairs of Helium. At Thark they part company and Dejah Thoris continues back to Helium. After arriving, Dejah Thoris has a strange feeling that something is wrong with Sola in Thark. So John Carter and Tars Tarkas journey together to rescue Sola.