The Sons of Garmadon

A year has passed since Master Wu was lost in time and the ninjas are spread across Ninjago but regroup when a powerful relic, the Oni mask of Vengence, is stolen by a group of masked criminals called the Sons of Garmadon. Lloyd finds that the group has something to do with his father, Lord Garmadon. Learning about the importance of the stolen 'Oni Mask' they are asked to protect the Royal Family and their Oni Mask from the Sons of Garmadon.

Lloyd and Princess Harumi venture through the streets of Ninjago City. Meanwhile, Cole finds out the Palace has been rigged with bombs. Just then, the Sons of Garmadon, led by Ultra Violet and the mysterious Mr. E, attack the Palace to steal the Oni Mask. Hutchins helps Lloyd and Harumi escape with the mask through a secret tunnel but remains behind. Lloyd and Harumi flee but are attacked by the Sons of Garmadon, who manage to steal the Oni Mask. Returning to Destiny's Bounty, Lloyd and Harumi reunite with the other Ninjas, who reveals to them that they are the only ones who managed to escape from the Palace's destruction.

The Ninja allow Harumi to live with them on the Bounty. Lloyd and Jay are told by Mistake, an old wise lady that sells tea, of the tale of The Realm of Oni and Dragons and that the Sons of Garmadon plan to use the Oni Masks to resurrect Lord Garmadon. Meanwhile, Cole and Zane manage to get Luke Cunningham to tell them the location of the Sons of Garmadon's hangout. They disguise themselves but Cole's cover is blown and he is captured, while Zane maintains his cover as "Snake Jaguar" and earns Ultra Violet's and Mr. E's, prompting them to bring him to the "Big Man".

Zane, undercover as "Snake Jaguar" is brought into the Sons of Garmadon's hideout in the subway, where he meets Killow, the "Big Man" responsible for accepting new members and who challenges Zane to a bike race. Before the race, Zane meets Cole in a cell and learns that the leader of the Sons of Garmadon is named "The Quiet One" Cole escapes with a baby believed to be the "key" to the final Oni Mask. The race starts, but Killow is called by Ultra Violet, who tells him that Snake Jaguar is a Ninja. The Sons of Garmadon attack Zane. Mr. E runs after Zane, as they approach a cliff, they jump off their bikes. Much to Zane's surprise, Mr. E is revealed to be a Nindroid.

After a battle with Mr. E, Zane is severely injured and left in the desert until the ninjas find him. While looking after the baby Cole found, they discover his blanket is a map to the Primeval's Eye, where the Oni Mask might be located. Meanwhile, a device Mr. E placed inside Zane makes its way to the power supply, cutting down the power in the entire ship. Pixal reveals herself to be Samurai X just before her hacked mech attacks. She ejects herself from it, causing it to fall off the ship, but Lloyd and Harumi fall off as well, using the map as a parachute. Meanwhile, Zane wakes up and destroys the spider, but the Bounty crashes into the jungle. Lloyd and Harumi venture into the Primeval's Eye to find the final Oni Mask.

While Lloyd and Harumi venture deep into Primeval's Eye, the other Ninjas attempt to fix the Bounty and discover that the baby is Wu, who is recovering from the power of the Reversal Time-Blade. Also, while attempting to reboot, they discover that the Quiet One is Harumi, but are stopped by the attack of the Sons of Garmadon. Meanwhile, Harumi and Lloyd find a boat and use it to travel along a river, but are attacked by a giant underwater creature, which wrecks the boat. They manage to escape from the monster and fall down the waterfall, where they find the Oni Temple.

Lloyd and Harumi enter the Oni Temple and, after passing by some paintings depicting the Oni and traps, the two eventually find the Oni Mask. However, after Harumi tells Lloyd to pick it up, he realizes that she is The Quiet One. He eventually defeats Harumi in battle, but she grabs the Oni Mask and uses it to defeat Lloyd, before leaving the temple. Meanwhile, the Ninjas have been tied up by the Sons of Garmadon, who have taken over the Bounty and used it to arrive at the Oni Temple, but they manage to break free. As the Ninja and the Sons of Garmadon prepare to fight, they are attacked by the underwater monster. The Sons of Garmadon escape aboard the Bounty with all Oni Masks and Lloyd, while the other Ninjas are left to deal with the monster.

The Ninja return to Ninjago and arrive at the Police Station to ask for help in stopping the Sons of Garmadon's plan. Meanwhile, the Sons of Garmadon bring Lloyd to the Temple of Resurrection, where the ceremony to resurrect Garmadon will take place. Harumi reveals that she captured Lloyd's mother, Misako, as she needs them both in order to resurrect Garmadon. At nightfall, the Ninja sneak inside the temple, while Harumi opens a portal to the Departed Realm and summons Lord Garmadon. The Ninjas use Spinjitzu to close the portal and defeat the Sons of Garmadon. However, the ceremony has been completed, allowing Garmadon to return to Ninjago.

Lord Garmadon returns to Ninjago and releases all the imprisoned Sons of Garmadon and Harumi encourages him to "achieve his true potential" by conquering his son. The Ninjas find out Garmadon has taken over Kryptarium prison and head there to confront him, but Lloyd, believing he is destined to fight his father alone, locks the other Ninja on the Bounty. Arriving at the prison, Lloyd confronts his father, and the two battle, while the Sons of Garmadon broadcast everything in front of all the people of Ninjago. After throwing Lloyd out of the prison, Garmadon unlocks his True Potential and leaves to take over Ninjago City.

The Ninjas find Lloyd and manage to save him, at the cost of his elemental powers. Garmadon arrives in Ninjago City and four of the ninja receive a package from Mistaké and leave to fight a stone giant Garmadon built, Colossus. Lloyd runs away with Wu but runs into Harumi. The other ninjas make it to the Bounty and arrive in time to rescue Wu but not Lloyd, who is captured by Harumi. Colossus shows up and crushes the Bounty, while Harumi forces Lloyd to watch, but the four Ninjas use the package, discovering it to be Traveller's Tea, and find themselves in the Realm of Oni and Dragons.