In the underground caves of Mineworld, the imprisoned human population is forced to dig for crystals under the cracking whips of the robot henchmen of the evil ruler Zygon. While mining, a prisoner named Orin unearths a sword with a jeweled hilt, and an elderly man named Hopps is stunned to see that the rumored weapon exists. Hopps instructs Orin to hide the sword, but before he can explain its power, he is killed by a guard. His granddaughter, Elan, mourns him, and Orin promises to take care of her. As Orin examines the sword, it begins to glow, producing a projection of an ancient man who tells of a world that exists above the mines where the humans are meant to live, and instructs that their freedom will come if they find the blade of the sword. When the message ends, the blade of the sword disappears, leaving only the jewel-encrusted hilt behind. A man named Raimo claims the message is a lie and that Hell lies above them. However, Orin is inspired to search for the blade, and Elan offers her help. Raimo threatens to turn them in to the guards, and fights Orin for the hilt. Orin knocks Raimo unconscious, and sets off with Elan. However, they are captured by guards and delivered to Zygon, who removes his mask to reveal his human face to them. Zygon strangles Elan to death, and is surprised to see the sword hilt in Orin’s possession. He strangles Orin, but the hilt burns Zygon’s hand, causing him to release his grip. Orin escapes as henchmen shoot lasers at him. When the beams hit crystals in the mine, they create an explosion, knocking Zygon and the guards unconscious. Orin embraces Elan’s body, vowing to find the world above. As guards pursue him, the mine caves in around Orin and he becomes trapped. Over time, he uses his laser beam to dig upward. While he sleeps, he is attacked by leaches, and as he scrambles to remove them, he falls down a cavern and drops his laser into the abyss. Cursing the sword hilt, Orin raises it above his head, and the ground opens up above him revealing the night sky. Orin climbs out and cries when he sees the stars for the first time. He wanders the surface of the planet, Trinia, and is amazed at the creatures and vegetation he sees. Soon, he is surrounded by robot-human “mandroids” who capture him in order to steal his body parts. Orin’s hilt comes to life and protects him, killing the creatures. As Orin flees, he is chased by mandroids, but soon rescued by a human named Dagg, who assumes Orin is a fellow crystal smuggler. When Orin reveals that he has escaped from Mineworld, Dagg does not believe him, asserting that robots have been mining the crystals for thousands of years. When Dagg is attacked by a giant swamp creature, Orin frees him using the hilt, which produces an invisible blade when he grasps it. Orin asks for Dagg’s help to rescue the people of Mineworld, but Dagg declares they are “even,” and refuses. However, when a patrol ship flies overhead, they take cover together in Dagg’s spaceship, Starchaser, where he introduces Orin to the ship’s talking computer, “Arthur.” Dagg takes Orin on his crystal smuggling mission, and flies to the Rabidamite Shipping Complex where a gun battle ensues. After landing, Dagg leaves Starchaser to fight the robot guards, while Arthur attaches the ship to a crystal transporter that hovers overhead, and steals its contents. Zygon emerges from the Shipping Complex and captures Dagg. Watching from above, Orin orders Arthur to fly to Dagg’s rescue. When Zygon attacks Dagg with a laser gun, Orin deflects the beam with his invisible blade. Returning to Starchaser, Dagg takes a fembot named Silica as his prize. As they fly away from Trinia, Orin worries about the young, blind brother, Kallie, he left behind. Dagg resets Silica’s fembot personality switch to make her attracted to him, and tells Orin that he makes his living selling the smuggled crystals, which are used as starship fuel. Elsewhere, Zygon sends word to his henchmen to find the sword hilt, and vaporize Orin. Dagg flies to the “den of thieves,” Toga-Togo, where he and Orin part ways. Searching for the mysterious sword blade, Orin wanders aimlessly, and asks a fortuneteller where to find it. The scam-artist tells him it is in the Nova Luna rainforest. Elsewhere, Dagg sells Silica to a slave trader. When Orin sees the fembot being auctioned off, he believes she was stolen from Dagg, and bids for her on Dagg’s behalf. When Orin cannot produce the money for his winning bid, the trader takes him as a slave, per the local laws. However, Dagg arrives and reluctantly pays the fee to have Orin released, and Silica is returned to him. Zygon’s men spot Orin, and he and Dagg quickly take off in Starchaser. Orin requests that they travel to the rainforest, but Dagg declines, and instead flies to the Vahjii Desert to conduct a crystal trade with a man named Farok. Farok’s henchman sees Orin’s hilt and recognizes him as a wanted man, but Dagg threatens the thug, preventing him from taking Orin as his prisoner. Dagg quickly departs with his chest of gold from the sale. Aboard Starchaser, a “starfly” appears, and Orin believes the glowing insect is trying to tell them something. The starfly directs them to the gold, and Orin finds a time bomb buried inside. Dagg circles back around and drops the explosive onto Farok’s camp, where it detonates, and agrees to take Orin to the rainforest. On their journey, they engage in another battle with Zygon’s troops, and when Starchaser is hit, Dagg makes an emergency landing. Orin is thrown from the spaceship and found in the woods by Princess Aviana. Meanwhile, Dagg is taken prisoner, and tortured by Zygon to reveal Orin’s whereabouts. At Aviana’s palace, Orin wakes, and tells the Princess of his escape from Mineworld. She, too, has no knowledge that a human civilization was being held captive in the crystal mines. Aviana recognizes the hilt from her history lessons, and takes Orin to the library where her computer identifies it from its inclusion in the “Book of Ka Kahn.” When a picture of their leader is displayed, Orin recognizes him as the man who appeared from the sword with a message. The “Book of Ka Kahn” tells the story of two men, 600 years apart, who freed their enslaved people from captivity using the sword. Orin learns the blade was lost on Trinia after it was used in battle to defeat a warlord named Nexus. Aviana plans to ask for help from her father, Morbro, the Supreme Governor of the Bordegon System, but her robot, Mizo, suggests that Morbro would deny helping a “wanted man.” She agrees to take Orin back to Trinia by herself. Upon arriving, Aviana leads him directly to Zygon, to ask for his help, unaware that he is responsible for enslaving the people of Mineworld. When Zygon attacks, Orin strikes with his invisible blade, and a cut reveals his robotic face. Zygon admits that his true identity is “Nexus,” the robot warlord who has reigned for over a thousand years. Orin and Aviana are imprisoned next to Dagg. Sometime later, Zygon plans an attack that would ensure his rule over the entire Bordegon System. Fearing a counter-attack from Supreme Governor Morbro, he plans to use Aviana to prevent her father from interfering. Orin laments his failure to find the sword and save his people, and Aviana shares her feelings for him. Before they can kiss, robots enter and take Aviana to Zygon. In time, a starfly appears in Orin’s cell, and he sends the insect to retrieve his hilt. Orin uses the magic sword to free himself and Dagg, and they secretly board a flagship departing for the Bordegon System, carrying Aviana. Meanwhile, Silica, the fembot, repairs Starchaser, and with the help of onboard computer, Arthur, they search for Dagg and Orin. Orin and Dagg take control of the flagship and rescue Aviana, who rewards Orin with a kiss. Back on Trinia, Zygon learns that his mission has been compromised, and sees the hilt is missing. A starfly appears on the flagship, and helps Orin and Dagg by repairing the broken control panel. Starchaser arrives, and together they thwart Zygon’s secondary attack on Bordegon, destroying his entire fleet. Orin demands they return to Trinia to free his people, and Zygon lies in wait. After crashing the flagship into Zygon’s headquarters, Dagg suffers a broken leg, and Orin leaves him and Aviana behind to go to Mineworld alone. Upon arriving, he tells the prisoners that a better world exists above ground, but they refuse to believe him. Zygon enters holding Aviana in his grasp, and demands that Orin give him the sword hilt. Orin hands over the hilt, but when Zygon strikes at Orin, the invisible blade does not appear. Zygon pushes Orin over a cliff, and as he dangles from the heights, a starfly arrives. Orin asks it to bring him the hilt, but the mystical creature asserts that he does not need it and declares there never was a blade. Zygon steps on Orin’s hands, but he pulls himself to safety, and with sheer will, materializes an invisible sword, and strikes down Zygon. The evil lord falls into the abyss, and Orin proclaims his people free. Meanwhile Silica accidentally crashes Starchaser into Zygon’s domain, and Mineworld crumbles down around the inmates. However, Orin throws the hilt above them and creates an escape route. The freed people marvel at the world above, and Orin’s blind brother, Kallie, asks him to describe it. Orin places his hands over Kallie’s eyes, and restores the boy’s vision. As Aviana and Orin kiss, starflies swirl around them, and transform into ancient members of the Ka Kahn. The elders congratulate Orin and invite him to leave his human form and join them, but Orin, looking at Aviana, proclaims he is not yet ready to do so.