Yugi and friends arrive at a lava-covered wasteland. The dangers of the place are evident when Tristan and Solomon Muto nearly fall in, but Joey is eager to find the clue for the next riddle himself. Tristan is doubtful, but Tea and Yugi are supportive, reminding him how Joey's enthusiasm brought them to the Capsule Monster world and found them the map.
When Joey wanders off, though, he's attacked by the Red-Eyes Black Dragon! Joey realizes something is odd about the dragon, since it doesn't seem to want to attack him, but he doesn't have time to puzzle out what it means as the attacks continue. Meanwhile, Tea and Dark Witch find the clue, which says to locate the peak that spits fire. The Blade of Chaos must be removed in order to bring peace to the land. Figuring the riddle means a sword at the top of the volcano, the group climbs up... but when Tristan slips and falls, being saved by a newly-claimed Thunder Dragon, they realize it'd be faster to use their Capsule Monsters.
The group reaches the peak and makes to pull out the sword, when suddenly they're attacked... by Joey! He fused with the Red-Eyes just like Yugi did with his monsters, and plans to complete the challenge alone. The group realizes he's under the control of an evil force. While Yami Yugi tries to bring him back to his senses, Tea, Tristan, and Solomon try to pull out the blade, which is sinking deeper into the rock. Joey isn't about to let that happen, though, and attacks Yami Yugi as well as his friends, knocking them down the mountain.
As they clash, the real Joey is able to communicate with Yugi in spirit form, saying that something was wrong with Red-Eyes Black Dragon before they merged. The only way to break the spell is to destroy the armor that's controlling him, which would destroy Joey too. The others try to defeat him, but can't bring themselves to attack their friend. Joey makes to finish them off, but the real Joey is able to seize control and stop himself from moving. Yami Yugi blasts the Red-Eyes armor off of Joey with an attack, and further stuns the dragon with Magic Cylinder—but by this point, the sword has fully sunken into the rock.
Joey reveals that they haven't failed the challenge yet, though, and runs up to the Red-Eyes. Straining with all his might, he pulls out a sword embedded in the dragon's back, which was the real Blade of Chaos—the sword on the peak was just a decoy. Yami destroys the sword, and the door to the next world appears. Thoroughly exhausted, but relieved to have saved his favorite monster, Joey claims Red-Eyes as his own as they depart.
This episode contains examples of:
- Brainwashed and Crazy: Joey and Red-Eyes Black Dragon become this thanks to the Blade of Chaos.
- "I Know You Are in There Somewhere" Fight: The second time Yugi does this with a possessed Joey. And once again, it works.
- Mind-Control Eyes: Joey gets crazed red eyes when possessed. Appropriate, as he's merged with the Red-Eyes Black Dragon.
