The episode begins with Jack walking through a destroyed village, where he finds an injured local who says "they came from nowhere" and also says "they left to the east." So, Jack goes east to find another destroyed village and a dying robot citizen who tells him the rest of the story. Jack continues east into yet another destroyed village that was also populated by robot citizens. This time, none of them are alive to tell him anything. But instead, Jack takes a look at their bodies and, in his mind, depicts how the mysterious things destroyed them and their village. A few dead robots seem to have multiple shuriken sunk into their bodies. Some other dead robots seem to have been sliced up, possibly with a sword. But Jack also finds tracks leading to the east. So, Jack follows the tracks to find eight identical baskets that transform into the Ultra-robots, one with Gatling guns for arms, one with flamethrowers for arms, one with buzzsaws for arms, one with a rotor in the center of its torso for repeatedly throwing shuriken, one that can launch its hand from its arm connected with a chain, one that can launch an explosive wire from its torso, one that uses its own fists to fight but can also turn invisible, and finally, one wielding a semi-futuristic katana. They tell him that their purpose is to destroy him and Jack engages them in battle but to no avail, with their diverse weapons and their solid metal (which Jack's sword can't cut) the Ultra-robots easily overpower Jack who has no choice but to run and seek shelter in the destroyed village up ahead.
While hiding, Jack meets the scientist Extor, the creator of the Ultra-robots, who explains to Jack what has happened. Aku needed more weapons to destroy Jack and told Extor that he would spare his village if he built him the ultimate weapons to destroy Jack. Extor built the robots from adamantium metal, fit each of them with different weapons and abilities, and spent days analyzing Jack's fighting skills. Aku himself provided the Ultra-robots power source by imbuing them with his own evil essence. But as he presented them to Aku, Aku betrayed Extor and sent the robots to destroy Extor's village as a test of their destructive power. Extor asks Jack for his help to destroy the robots, but Jack says he can't help him due to the fact that his sword can't cut the robots and even says that "Aku has finally won."
Extor gives Jack a mechanical power gauntlet that can enhance his strength to destroy any type of metal, even the admantium that the Ultra-robots are made of. In a rematch with the Ultra-robots, Jack manages to destroy seven of them using the cyborg arm. But the arm's battery eventually dies and the arm becomes useless. So when Jack realizes that last Ultra-robot left is the katana-wielding one, he discards it and prays to his ancestors to give his sword more power. Just as the Ultra-robot prepares to drop his blade on Jack, the samurai's wish is granted and he manages to slice the last Ultra-robot in half whole last words are "Unbelievable".
Jack notices Aku's essence leaving the debris of each Ultra-robot and quickly uses his sword to destroy it. Elsewhere, Aku exclaims in pain, knowing that Jack and his sword are the cause. As he sheathes his blade, Extor goes to congratulate Jack with a high five.
- Casting by
- Collette Sunderman
- Goof: When Jack finds the only surviving robot in the second village the robot's neck is only hanging on to what's left of its body by a few wires. But when the robot's flashback ends its neck is completely intact.
- Goof: The interior design of the building where Jack hides from the Ultra-Bots is inconsistent.