Dark clouds gather over Ninjago City, forming a huge vortex in the sky. Dareth, Lou, and the others assume that the Ninja have returned, but the Garmatron appears instead.
Determined to protect the city, Dareth challenges the advancing tank, but the Overlord drives him off with a few shots from the tank's side-mounted turrets.
As a corrupted Nya looks on and Dareth wonders where the Ninja are, the Garmatron continues to fire shots into the city, spreading Dark Matter everywhere—atop the tank, massive wings emerge from the Overlord's back.
Aria stands next to her father and watched over everything. It's gotten way ouy of hand for her.
"Daughter, it's time for your transformation" the Overlorf said
"Right..." Aria said softly as she let her father's dark energy combine with her own and start her transformation.
Back on the Island of Darkness, Jay wonders if they'll see Nya again, and Master Wu admits to Kai that for once, he has no words of wisdom to give, Aria's was the best they had.
Lloyd rallies his friends, reminding them how they brought him from the path of evil to become the Green Ninja.
He believes that there must have been a reason why they were chosen to carry on the legacy of the First Spinjitzu Master: they're ninja, and ninja never quit.
The Ninja are heartened by the speech but realize that they still have no means of reaching Ninjago. Kai is preparing to swim across the Endless Ocean himself.
"If Aria wanted to help, she should've let us through her portal" Kai said
"But then she would be going against her father, and just because he doesn't hate her doesn't mean he won't hurt her" Cole said
"So the Overlord would hurt his own daughter?" Jay asked
"Sadly, yes the Overlord would do whatever it takes to get what he wants" Wu said
"That's wrong, Aria's being used" Lloyd said angrily
Zane looks up and sees the Falcon gliding down to meet him once more. Deciding that the mechanical bird wants to show them something, the heroes follow the Falcon in Kai's Fire Robot, back to the Temple of Light.
Cole wonders why they have returned, but Misako finds an area of the temple resembling a picture in one of her scrolls.
When the Ninja insert their Elemental Blades into the four slots around the room, the center of the floor opens up to reveal a large golden mech. Misako identifies it as the fighting suit used by the First Spinjitzu Master to battle the Overlord.
Dr. Julien notes that the eons have reduced it to a non-functional relic. Master Wu believes that Lloyd can remedy that—sure enough, the Green Ninja's presence in the cockpit restores the mech to its original state.I
Learning that the mech can fly, Misako quips that at least one of them can now reach Ninjago. On cue, the Ultra Dragonarrives, and the other heroes use it to accompany Lloyd back to Ninjago City.
However, Ninjago City is not as they remember; everything is shadowy, the people are apathetic puppets of darkness, and a massive tower dominates the skyline.
Master Wu identifies the latter as the Garmatron, transformed into a fortress by the Overlord. Moving to the ground to get a better look, the Ninja narrowly avoid being hit with a blob of pure darkness—atop the tower, a massive black dragon roars to the sky.
Misako realizes that the Overlord has finally regained his original form, and the group makes an attack plan: most of them will draw the Overlord's attention with the Ultra Dragon, while Lloyd takes the Golden Mech to fight the ultimate evil head-on.
"But where's Aria?" Cole asks
"As the Overlord's most powerful weapon, Aria is most likely being guarded by her father" Misako said
"Weapon? What do you mean?" Lloyd asks
"Aria is his daughter, she has the power of darkness inside her so she herself can transform as well" Misako said
"But their's only one dragon up there" Jay said confused
"Aria has a different form, she does not turn into a dragon" Wu said
"Aria's not some tool he can just use however he'd like, she's his daughter!" Lloyd shouted angry
The tower is guarded by Kozu, at his command, the Stone Army opens fire on the Ultra Dragon. Lloyd uses the distraction to advance on the tower by foot, cheered on by Dareth, who has managed to avoid the corruption.
The Golden Mech breaks through the outer wall of the fortress and begins battling the Stone Army, only to be destroyed when Nya attacks it with a mobile defense turret. With the Green Ninja pinned down, the Ninja jump off the Ultra Dragon to fend off the advancing Stone Army.
Master Wu prepares to lead the Ultra Dragon into the battle, but Misako tells him that there are too many Stone Warriors to defeat. Another option presents itself when she notices that the Overlord is no longer wearing his helmet, she quickly explains to the other two that whoever wears the Helmet of Shadows controls the Stone Army.
The older trio sets off in search of the helmet, only to see Dareth putting it on his head; back at the fortress, the Stone Army freezes moments before they can deliver the final blow to the Ninja. General Kozu declares "All hail the Brown Ninja!" and the Ultra Dragon lands in front of the bewildered Ninja to allow Dareth to dismount.
Impressed by the turn of events, Kai officially welcomes Dareth as a ninja before the group prepares their final push against the Overlord.
Dareth sends the Stone Army up the staircase surrounding the fortress, but Nya shoots them down with her turret. The Ultra Dragon draws Nya's fire long enough for the Ninja to begin climbing the stairs but are forced to land when a shot clips its tail.
Meanwhile, the Ninjas' numbers slowly dwindle due to their enemies' relentless assault; Jay and Cole are corrupted by the Overlord's darkness, Zane stays back to fight them, and Kai attacks Nya's turret to keep her occupied, leaving Lloyd to go up to the roof on his own.
The Overlord turns his attention to the Green Ninja as he dons his mask and declares his intention to fight. The Overlord asserts that evil has won—Lloyd is alone, injured, and unarmed, but Lloyd charges his powers.
"I will never give up, now where's Aria" Lloyd said determined
"Right where she should be, by my side" the Overlord said lifting up his wing to show Aria.
The Overlord bombards the Green Ninja's energy shield with a gout of dark fire, but Lloyd pushes back, dispelling the flames. Aria stood up and shot dark fire with her father.
"Aria stop! Your better then this, i know you are, please" Lloyd shouted desperately
"I am the Overlord's daughter, and that's all i will ever be" Aria cried, her flames becoming stronger
"Aria please, come back to me, you know who i am to you Aria!" Lloyd shouted
"he remembers" Aria mumbled, her eyes becoming their usual green color and her hair turning blonde
"No!" the overlord shouted
Aria stopped shooting dark fire and ran over to Lloyd. Lloyd wrapped one of his arms around her waist and turned to the Overlord.
"I'll be taking my friend back now" Lloyd said
"Lloyd Garmadon i swear if you put your hand any lower i'm going to slap you" Aria said
"Aria, ruining the mood since she was 3" Lloyd laughed a bit
"Shut up" Aria said slightly annoyed
"You are my daughter! You belong with me!" the Overlord shouted angry
"She's not some tool that you can use!" Lloyd shouted ad his suit becomes golden as he finally unleashes his True Potential.
Below, Misako says "He has become the Ultimate Spinjitzu Master"
"the true final battle has begun" Wu said as Lloyd's energy flowed into Aria, activating her golden energy
"I am the Ultimate Spinjitzu Master!" Lloyd declared taking Aria's hand
The Overlord attacks, but Lloyd strikes back, knocking him off the roof and manifesting a Golden Dragon of pure energy to take to the air. Aria was sitting behind him on the dragon with her arms around his waist.
"Where their is light, their will always be darkness" The Overlord snarls
"unless our light is bright enough" Lloyd retorts looking at Aria
The golden dragon tackles the Overlord, flying all around the fortress before the villain can break free.
Infuriated at Lloyd's persistence, the Overlord uses his ultimate attack, engulfing the Green Ninja and his daughter in a sphere of pure darkness.
Within the sphere, Lloyd and Aria and the dragon are spun around before being swallowed by a giant Overlord, but Lloyd and Aria charges their powers and overwhelms the ultimate evil from within.
With a final roar of fury, the Overlord is destroyed, creating a wave of light that removes the darkness tainting Ninjago.
In the crater where the Overlord's fortress used to be, Kai awakens to find that both Jay and Nya are back to normal.
The Ultra Dragon lands near Cole and Zane, and Dr. Julien wonders if they really did it—in response, Dareth says they all did it.
Misako and Master Wu congratulate Lloyd as he descends and dismisses his dragon, Aria standing away from all of them, with the Ninja vowing to be ready if the Overlord ever does try to return.
Lloyd's mood quickly turns melancholy, however, as Misako tells him that everyone will miss his father.
On cue, a pile of rocks shift, and a man about Master Wu's age emerges to call Lloyd. Recognizing the voice, Misako and Lloyd are stunned—Garmadon has returned, completely purified of evil.
Master Wu tells his brother that it is good to have him back, and Garmadon replies that it's good to be back.
As the former villain walks off with his wife and son, Jay contemplates a friendly dogpile, but Kai tells him to let the family have their moment.
With evil firmly defeated, Cole tells his friends that they had quite an adventure together. Zane wonders if there will be others; Cole hopes so, as he enjoyed being a Ninja, and he's not sure if they have any other skills.
Jay objects to the contrary, and Kai agrees "new challenges and enemies might emerge one day, and as long as there's something worth fighting for, there'll be a need for ninja"
Master Wu smiled and walked over to Aria "my dear, you have grown up"
"I have sensei, how long has it been?" She asked sadly
"Wait what?" Kai asked confused
"Back when Aria was 6 she was one of my pupils" Sensei said
Lloyd hugged Aria "i remember everything you know"
"Are you sure about that?" Aria asked
"Of course cupcake" Lloyd said and Aria's face turned red
"Someone's blushing" Cole said teasingly
"Shut up stupid cousin" Aria said embarrassed
"Get over here Aria" Zane said
"Yeah your part of the team now too" Jay said happily
"I-I am?" Aria asked unsure
"Of course" Kai said
Lloyd grabbed her hand and brought her over to the rest of the guys. Nya, Misako, Garmadon, and Wu stood together watching them.
Kai, Jay, Zane, Cole, Lloyd, and Aria all put their hands together and shouted "Ninja go!"