John Carter Edgar Rice Burroughs attended John Carter’s funeral in 1881. John Carter was a former American Civil War Confederate Army Captain who suddenly died. The body is placed in an unmarked tomb that can only be opened by the inside, according to Carter was instructed. The attorney of Carter gives his personal journal for Burroughs to read.
In a flashback to the year 1868 in the Arizona Territory, Union Colonel Powell takes charge of Carter with the hope that Carter can aid in the fight against local Apache. Carter escapes from his cell only to be resuscitated by U.S. cavalry soldiers who are right behind. After a confrontation with Apaches, Carter and Powell are chased by U.S. cavalry soldiers until they find an underground cave brimming with gold. At that point, a Thern emerges from the cave and, frightened by the men, attacks the group with an axe. Carter then kills him however, he accidentally activates Thern’s powerful Medallion. He is then taken to Barsoom which is a dying planet which is known to Carter as Mars. Due to his differing bone density, as well as the planet’s low gravity, Carter is able to leap high and do feats of incredible power. The Green Martian Tharks take him in and Tars Tarkas and their Jeddak.
The Red Martian cities Red Martian of Helium, Zodanga and Barsoom are at war for more than 1000 years. Sab Than, Jeddak from Zodanga, is equipped with a specific weapon he obtained from Matai Shang and proposes a ceasefire. He also proposes that the war be ended by Dejah Thoris, Princess of Helium. Carter rescues the Princess and she escapes.
Dejah, Carter and Tarkas’s little girl, Sola, find a location in a sacred river to assist Carter return to Earth. They discover that the medallions are powered by the “ninth ray” that is also the source for Sab Than’s weapon. The Warhoon are a ferocious race under Shang’s control, attack them. Carter and Dejah are then taken back to Zodanga. The two are demoralized. Dejah is reluctantly able to marry Sabthan, and provides Carter instructions for how to use the medallion in order to return to Earth. Carter decides to stay on and is captured by Shang who informs him of the motives of Therns and how they manipulate the world’s civilizations to the point of extinction, feeding off the resources of the planet as a result. They are planning to do the exact way with Barsoom. They decide to choose Sab Than to be the ruler of the planet. Carter goes back to the Tharks along with Sola to seek their assistance. They find out that Tarkas was killed by Tal Hajus who is a vicious brute. Carter and injured Tarkas battle with two enormous Great White-Apes in an arena before Carter is killed by Hajus, thereby becoming the leader of the Tharks.
The Thark army swarms towards Helium and defeats the Zodangan army, while Sab Than is killed. Shang must flee. Carter is made the prince of Helium through the marriage of Dejah. In their first night, Carter decides to stay for the rest of his life on Mars and throws away his medallion. In the midst of this, Shang briefly reappears and presents Carter another challenge, sending Carter back to Earth. Carter begins an extended search to locate one of the medallions. He seems to have passed away suddenly after a few years and has requested unusual funeral arrangements. This is in accordance with him having found an award. As the return of Mars could leave Earth in a coma-like condition, he makes Burroughs his the one to protect him.
Back in the present, Burroughs runs back to Carter’s tomb , and uses clues to find the way to open it. As he is doing so, a Thern is seen and raises a gun before Carter appears and shoots the Thern in the back. He reveals that he had never found another medallion; instead, he devised an elaborate plan to lure Thern Thern from hiding, thus winning Shang’s challenge. Carter then utilizes the medallion of the deceased Thern to return to Barsoom