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.
Nya states in The Last Resort that she saw a future with Jay the first time she met him, which took place in this episode.
When the ninja try to help Wu when he is battling Samukai, Kai says, "No. This is Sensei's fight". A similar sentiment would eventually be used on Kai in The Invitation, when he was battling Karlof and Master Garmadon told the other ninja not to get involved, because "Kai started this. He can finish it".
Some airings of this episode place King of Shadows and this one together as a single episode, due to the combined time length being 20 minutes, the normal length of an episode.
In a concept for the pilot's original ending, the ninja followed Garmadon into a portal to the future.
In one shot of Wu's fight with Samukai, a lightning Skulkin is lying on the ground despite them all being knocked away in an earlier shot.
When Zane jumps into the fortress, he is holding the Shurikens of Ice instead of his regular shurikens that he wields in the rest of the episode.
When the ninja are riding above Ninjago on the dragons for the first time, Jay shouts even though he was voiceless at the time.
Near the end, while Wu is imploring Garmadon to surrender, his voice gains a Japanese accent.
Paul Dobson confirmed in his interview with Brent Miller that he re-recorded his lines for Wu in the pilot episodes because the original voice "was deemed politically incorrect". However, the original version of this one line was left in by mistake.
During Wu's fight with Samukai, Jay somehow manages to eat a stick of cotton candy, even though his mask is on.