John Carter, a jaded Civil War veteran tired of fighting, finds himself transported to the mysterious red planet Mars (known as Barsoom). There, he discovers a dying world caught in a centuries-long war between different tribes. With his Earthly strength surprisingly enhanced by the thinner atmosphere, he leaps great distances and becomes embroiled in the conflict.
He encounters Princess Dejah Thoris, captured by the rival city of Zodanga. Carter joins forces with the Tharks, green-skinned warriors led by the noble Tars Tarkas, to rescue her. He learns of Barsoom's dying state, caused by the abuse of a powerful energy source called the Ninth Ray.
As events unfold, Carter finds himself torn between returning to his old life and aiding the Barsoomians. He discovers a connection to the planet from a past life and unlocks his true potential. He must use his newfound abilities and unite the warring factions to save Barsoom from destruction and secure Dejah's freedom.