It's night time in Eternia, a six-legged lizard sneaks into the Royal Palace dungeon where the guards are playing Eternian Chess. The lizard gives the keys to a specific prisoner without the guards knowing. A small, furry, white creature in another cell with yellow cat-eyes watches. The prisoner frees himself and removes his muzzle. He attacks the guards right before one of them sounds the alarm and the prisoner escapes. Man-At-Arms arrives at the scene and identifies the prisoner as Kobra Khan and sends the guards to look for him. The witnessing prisoner tells him that they'll never catch him.
Outside, Kobra Khan emerges from the sewer and sneaks up on a guard and steals his Wind Raider.
Minutes later, Kobra Khan and his pet lizard arrive near Snake Mountain where he announces his plans to release King Hiss. All of a sudden, he is brought to Skeletor by Mer-Man and Two-Badd as an intruder. Kobra Khan asks for his service to help get revenge on Eternia and Skeletor agrees.
At Man-At-Arms' workshop, Man-At-Arms tells Prince Adam, Teela, and Orko that Kobra Khan is going to Snake Mountain to free King Hiss and the Snake Men. Adam thought it was a legend and Man-At-Arms tells them the story:
In the past, King Hiss and his Snake Men dominated part of Eternia from there fortress within Snake Mountain. They would've succeeded if it weren't for the combined powers of the Elders and the mystic Zodak. They imprisoned King Hiss and the Snake Men in a void within Snake Mountain.
Man-At-Arms tells Teela and Adam that the Sorceress asked him to seek Zodak's help and they leave to his retreat in the Mystic Mountains.
At Snake Mountain, Kobra Khan and Skeletor are walking around within. Kobra Khan asks Skeletor where a certain hallway leads, but Beast Man says it's none of his business.
Meanwhile, Man-At-Arms lands the transport due to the altitude and they continue on foot. They arrive at Zodak's house where Zodak was meditating. Man-At-Arms apologizes for the intrusion and introduces himself, Adam, and Teela. He tells Zodak about Kobra Khan's plot. Zodak uses his psychic power to move the staff to his hand and gets on his floating chair. Man-At-Arms asks Zodak for their help, but he tells them he will go...alone.
Back at Snake Mountain, Kobra Khan is showing Skeletor, Evil-Lyn, Beast Man, and Tri-Klops the weak points of the Royal Palace. Skeletor explains his plot to them while Kobra Khan sneaks away. Kobra Khan makes his way down a hallway he saw before.
On their way to Snake Mountain, Man-At-Arms tells Teela and Adam that King Hiss killed Zodak's brother. Adam and Teela think that Zodak might not get passed Skeletor and his warriors. Man-At-Arms tells them not to underestimate Zodak....He can see into his enemy's weakness.
At Snake Mountain, Zodak takes out Tri-Klops and enters Skeletor's chamber asking for them to turn over Kobra Khan. The villains laugh and attack, but are beaten. Evil-Lyn says a spell which pins enemies to the wall, but Zodak reflects it with his staff and Skeletor, Evil-Lyn, Beast Man, Mer-Man, and Two-Badd are pinned to the wall instead. Zodak heads out to find Kobra Khan while Skeletor tries to call his Havok Staff.
Kobra Khan unlocks a doorway that leads to the void where King Hiss and the Snake Men are imprisoned. He is watched in the shadows by a spider-like being.
Man-At Arms, Teela, and Adam arrive at Snake Mountain to find the evil warriors [except Skeletor] pinned to the wall and knowing it's Zodak's work.
Kobra Khan arrives at the void and places the Snake Men key into one of the structures and the void is opened. Zodak arrives to fight Kobra Khan. Kobra Khan's hood expands and shoots acid at him. Zodak throws off the mask before it melts and is knocked into the structure. A Snake Man by the name of General Rattlor emerges from the void and plans to feed Zodak to King Hiss.
Just then, Man-At-Arms and Teela come to the rescue and knock away General Rattlor. Rattlor calls for the Snake Men to appear while Adam runs down a hallway. Kobra Khan melts the doorway to prevent Teela from following as she is attacked by the Snake Men.
Adam transforms into He-Man and joins the fight. He-Man chases after Kobra Khan from structure to structure before being blasted into the pit by the Havok Staff with Zodak following He-Man. Kobra Khan hangs from the side with Skeletor on the edge.
In the pit, He-Man is far from his sword as he is grabbed by the Snake Men inside the pit.
Outside, Man-At-Arms and Teela are battling Skeletor and the Snake Men. Skeletor thought that Kobra Khan recruited the Snake Men for his army and congradulated him.
Inside the pit, Zodak arrives and finds He-Man's sword. The Snake Men bring He-Man to a shadowy figure identified as King Hiss as he is coming to. Zodak rescues He-Man and the shadow of King Hiss commands his Snake Men soldier to attack while turning into his Snake Man form.
During the fight, Kobra Khan tells Teela and Man-At-Arms that King Hiss will rise up and rule Eternia not knowing that Skeletor was nearby when he said that. Zodak and He-Man emerge from the pit. Kobra Khan melts where the key is preventing them from removing it. The two combine their strength and damage a structure causing the Snake Men to be sucked back into the pit and be sealed in it. Kobra Khan and General Rattlor go down another hallway with Kobra Khan saying that King Hiss will rise again and Skeletor goes down another.
Back at the Royal Palace, Zodak thanks Man-At-Arms, Teela, and Adam for their help. Man-At-Arms tells Zodak that they'll need his help in future crisis'. Zodak is now an ally to the Masters.