During the Hyborean age, "a time of high adventure," an unseen blacksmith creates a masterwork sword. The sword is completed, and it is clear that the blacksmith is Conan's father (William Smith). Conan's father explains to young Conan (Jorge Sanz) about their god, Crom, who lives in the Earth and that he should not trust men, woman, or beasts, "But this you can trust," indicating the sword he has crafted. Cut to Conan's forest village. It is winter, and Conan is still young (8-10 years).
Mysterious black riders, bearing a strange standard of a serpent with a head on each end surmounted by a black sun and moon, suddenly and savagely attack the village. The villagers fight bravely, but they are not soldiers, and do not last long. Conan's father kills several of the attackers, but eventually succumbs himself. As the brutal attack winds down, Conan's mother (Nadiuska) is the only adult still alive. She stands guard over Conan with her own sword, holding the little boy's hand.
The leader of the attackers, Thulsa Doom (James Earl Jones), a mysterious black man with straight hair and piercing blue eyes, approaches the pair with his two hulking lieutenants, Rexor (Ben Davidson) and Thorgrim (Sven-Ole Thorsen). Conan's mother stands her ground bravely but is hypnotized by the piercing eyes of Doom. Doom, having taken Conan's father's sword from Rexor, suddenly wheels and beheads Conan's mother.
A grief stricken and terrified Conan watches as Thulsa Doom keeps the sword his father made. Conan and the village children, the only survivors, are led away in chains as slaves while their village burns. Conan and some of the children are sold and join other children at a gigantic outdoor grain mill, called the Wheel of Pain. They begin pushing the spokes of the wheel, and time passes quickly.
The child Conan becomes an adult (Arnold Schwarzenegger) and the camera pans out to show that he is now the only one left pushing the wheel. Conan has become enormously muscular by the time the mill is shut down and he is led away in chains. Conan is purchased by a large, red-haired warrior (Luis Barboo) who employs him as a sport fighter. At first Conan is puzzled by the violence, but quickly learns hand-to-hand combat with a variety of weapons. He becomes a champion, winning much gold for his master.
His master sends in young beautiful women into Conan's secured dwelling regularly, for him to bed. We see a young woman thrown in his cage, she's initially terrified of Conan. It's clear this brings him great pleasure as he approaches her with gusto, but he also treats her gently. His master then takes him to the Far East where he is trained in all manner of combat skills, weaponry, and philosophy.
Finally one evening his master, who is clearly drunk, decides to free him. The now free Conan finds himself being chased by wolves across the country-side. Climbing a cairn of rocks for safety he discovers the tomb of an old king and liberates his ancient sword and other equipment for protection.
Now equipped with the basics, Conan travels till he comes to the hut of a beautiful woman who appears to be a witch (Cassandra Gava). See invites him in and she offers to tell him his fortune. Conan says that he's looking for a a symbol of a single serpent with two heads that face each other. Later while they make love she cries out that Conan will find the symbol in the land of Zamora. Moments later, she shifts into a demon and Conan is forced to throw her into the fire. She explodes in flames, turns into a fireball and races around the hut and out through the surrounding woods.
The next morning, he finds a man chained behind the hut. His name is Subotai (Gerry Lopez) and he is a thief. Conan releases him and they team up. Subotai introduces Conan to thievery as a profession and they move from town to town practicing their trade. Conan is always asking if anyone has seen the strange serpent symbol. One old man tells them that there is a snake cult of growing power with temples in many towns including this one, but he does not know if they use the symbol he seeks.
Subotai and Conan decide to raid the temple, rumored to have great treasures including a huge ruby called the "Eye of the Serpent." As they prepare to climb the temple's tower they become aware of a woman in the shadows. Confronting her, they find out that she is also a thief, named Valeria (Sandahl Bergman). They decide to join forces.
After climbing the tower Valeria checks out the upper level while Conan and Subotai continue down into a pit containing the "Serpents Eye" guarded by a humongous snake. Fortunately the snake sleeps while the two steal all they can. On the upper level a ceremony is taking place presided over by Rexor.
There, a young girl (Leslie Foldvary) strips and prepares to throw herself into the snake pit to be consumed by the serpent as a sacrifice. Conan is leaving when he sees a medallion on the wall that matches the symbol of Doom's marauders that destroyed his village. He steals the medallion, however, he lingers too long and the snake awakes and attacks. He and Subotai manage to kill it, however, without disturbing the ceremony at the top of the pit.
The ceremony reaches its climax and the girl throws herself into the pit. It is only then discovered that the snake is dead. Rexor send guards after the thieves, but they escape. Over the next days the three thieves celebrate too hard and are easily captured by the King's guard.
Brought before King Osric (Max von Sydow) they expect punishment, but are surprised when the King congratulates them for standing up to the cult. He commissions them to go after his daughter (Valérie Quennessen), who has been seduced by the cult and travels to meet its leader, Thulsa Doom.
Valeria, who has fallen in love with Conan, does not want to risk their current happiness and advises against going after the princess. She awakens the next morning to find Conan gone.
He travels alone to find Thulsa Doom not just to rescue the princess, but also to avenge the murders of his parents and clan. Conan travels to Thulsa Doom's "Mountain of Power" temple in the east. Before he arrives he comes to a sacred place with many standing stones attended by an old wizard, Akiro (Mako).
They quickly become friends, and the wizard warns Conan of Doom's power. Conan disguises himself as a follower and goes to the temple.
The temple consists of a massive set of steps up the side of the mountain leading to an ornate entrance into caves that honeycomb the peak.