In the world of Barsoom, the vibrant Martian cities of Helium and Zodanga have been embroiled in a devastating war for a millennium. The malevolent Jeddak of Zodanga, Sab Than](/actor/dominc-west), wields a powerful weapon gifted to him by the Thern leader, Matai Shang (Mark Strong). This weapon supposedly empowers Than, declaring him the choice of the Goddess destined to rule uncontested. With it, he devastates Helium and proposes an end to the war by offering to marry the beautiful Princess of Helium, Dejah Thoris. However, Dejah is not merely a pawn; she is also a brilliant scientist who has created her own weapon utilizing the enigmatic 9th ray of the sun, offering a potential source of limitless energy. Unfortunately, her invention is sabotaged by a spy from the Therns, reinforcing her disdain for Sab Than.
The narrative also follows the late John Carter](/actor/taylor-kitsch), a former Confederate Army captain, whose unexpected death sends ripples through his family. His nephew, Edgar Rice Burroughs (aryl Sabara), attends the funeral and discovers a journal from Carter that may reveal the truth behind his uncle’s demise. The journal recounts Carter's past in the Arizona Territory, detailing how he was arrested by Union Colonel Powell (Bryan Cranston), and how their paths unexpectedly intertwine during a precarious escape from authorities while seeking riches.
As Carter explores a cave rumored to contain gold, he encounters a Thern and kills him in self-defense. In a twist of fate, Carter is inexplicably transported to the ancient planet of Barsoom. Owing to his Earthly physiology and the low gravity of Mars, he excels in incredible physical feats that astonish both friends and foes alike. He is soon captured by the Green Martians, ruled by Jeddak [Tars Tarkas.
Princess Dejah, meanwhile, escapes from her captors in a Helium ship only to be pursued by Sab Than’s forces. During her flight, she is rescued by Carter, who realizes that she is human and starts to bond with her. Sab Than, however, wants Carter alive and attempts to capture him—an effort complicated by the Tharks' increasing interest in Carter's remarkable abilities.
Dejah, desperate to leverage Carter's unique traits, proposes an alliance with the Tharks to combat Zodanga, yet they face internal politics when Tars Tarkas prefers to exploit Carter for his own ambitions. Tars finds himself in a precarious position, revealing a shocking family secret—that Sola, his daughter, is tasked with guarding Dejah and Carter in a forbidden temple. When they find themselves threatened, Tars implores them to flee and guides them toward the sacred river Isus, hoping to discover answers.
Carter, Dejah, and Sola’s quest leads them to the river’s end where they uncover an ancient mechanism that responds to Carter's medallion. Dejah deftly realizes that the 9th ray can be expressed through coded instructions, revealing immense power and the secret to returning Carter home. However, danger lurks from Shang, who suddenly attacks, driven to thwart their quest as he sees Carter approaching the Thern’s hidden truths.
In a dramatic turn, Carter battles the Warhoon army single-handedly when aid arrives. Sadly, Dejah’s father, influenced by Sab Than, pulls them back to Helium, and the heartbroken Dejah reluctantly prepares to marry Than. However, she entrusts Carter with the means to return to Earth, believing she will never see him again.
Yet, Carter’s resolve steers him to remain and combat the impending threat of Sab Than, setting him on a course filled with treachery and peril. Captured by Shang, Carter learns of the Therns' insidious motivations. After a daring escape, he and Sola find themselves in the midst of a brutal trial where Carter must face formidable creatures to win back his place among the Tharks, emerging victorious and rallying their forces.
The final conflict sees the Tharks wage war on Helium, leading to the defeat of Sab Than. In a moment of triumph, Carter marries Dejah, embracing his new life on Barsoom. Yet, fate intervenes as Shang finds a way to banish him back to Earth, prompting Carter to tirelessly search for the Therns’ presence there, concocting a unique funeral scheme to secure his return to Mars.
The narrative then pivots back to Edgar Burroughs, who, intrigued by Carter’s tumultuous story, rushes to his tomb only to discover it vacant. A confrontation with Shang follows, and in a stunning twist, Carter reappears, ready to reclaim his destiny on Barsoom armed with the knowledge he has gained along his incredible journey.
