Sensei Wu awakens in the Underworld, his journey having knocked him out. He picks up the Sword of Fire and begins to search for Lord Garmadon.
Cole, Jay, and Zane go to the Fire Temple to look for Kai and Sensei Wu, but Zane's sixth sense tells them they are not there. After Zane informs them of the news, the Fire Temple opens up, revealing Kai and Nya on top of the Fire Dragon. When he explained to the Fire Dragon that they were trying to protect the Golden Weapons, they became allies.
Nya states that Dragons can cross into the Underworld, although before they can leave, Kai asks Nya to wait back at their father's shop for them, to which she agrees. Afterward, out of his fear of Dragons, Cole claims there is no room on the Fire Dragon for the four of them to travel, giving Kai the idea to recruit the other Dragons. After they cross over to the Underworld, the four try to sneak past the Skulkin by using the stalactites from the ceiling, but they eventually find themselves hanging onto the legs of a Spykor, causing them to fall and alerting the Skulkin of their presence. Seeing there is no way out of fighting all the Spykor and Skulkin, Jay exclaims they should use the Tornado of Creation, gaining his voice back.
Sensei Wu soon finds Lord Garmadon, who commands Samukai to attack his brother. The four Ninja defeat all the Skulkin and rush to their Sensei's aid. The Ninja find Sensei Wu losing to Samukai, although Kai prevents the team from intervening, claiming it is Sensei Wu's fight. After Sensei Wu is defeated, Samukai betrays Lord Garmadon and takes all four Golden Weapons; however, Samukai is not strong enough to possess the four weapons at once, creating a portal and destroying him in the process. Lord Garmadon steps through it, leaving the Golden Weapons behind, although Sensei Wu mentions that Garmadon will return someday. Back at Four Weapons, the Ninja return safely to find Nya waiting, and everyone celebrates their temporary victory after the Ninja accidentally high-five each other with their Golden Weapons.
The episode was originally paired with "King of Shadows" as one episode. They were later split into two when released to LEGO.com.