Decoded is a series of Ninjago: Masters of Spinjitzu shorts taking place between season seven and season eight of the series, in which Zane's efforts to create a digital backup of his memory unearths a mysterious puzzle known as "the Ninjigma." The episodes consist primarily of clip shows from the series, though with sequences of new dialogue.
Vehicles and Mechs
After Zane becomes trapped in his memories, Nya uploads Jay's consciousness into the computer network in an effort to find him. They uncover a puzzle that resembles a vehicle schematic.
With Jay and Zane both trapped in the computer, Nya sends Cole in to try and help them, and the four examine a collection of location images. They eventually determine that the key locations are ones where they've lived, and that the solution to the puzzle is the order in which they lived in said locations. Unfortunately, solving the puzzle reveals that Zane's systems are being hacked by an unknown adversary.
Ninjago's Most Wanted
Nya brings in Kai to join the other three ninja in Zane's mind in an effort to save him from whatever hostile force is hacking into his systems. The latest aspect of the Ninjigma involves their past foes, with the Ninja trying to identify which of them might be responsible for Zane's condition. However, Nya then interrupts the boys with a warning that something is attempting to penetrate the Samurai X Cave, and pulls Cole out to address the threat.
The Digiverse and Beyond
Without Cole, the other three boy ninja attempt to work through a puzzle regarding various technologies they have encountered, including Nindroids, the Falcon, and the still absent P.I.X.A.L. Unfortunately, after solving the technology puzzle, Nya determines that the hostile force invading Zane's systems is attempting to take control of him.
The Elemental Masters
The Ninja move on to the next puzzle, which is a riddle surrounded by the symbols of the Elemental Masters.
Beasts and Dragons
As Cole continues to deal with the mysterious attacking monster, which has destroyed one of the cave's power generators, the other ninja continue their attempts to solve the Ninjigma. The subject of their attacker prompts consideration of the various creatures they have encountered, while Cole determines that the beast has electrical powers. Eventually the beast destroys another generator, but Cole is able to stop it with a cave in. However, Zane's body then awakens with glowing red eyes and a strange voice and menaces Nya.
Rise of Garmadon
The Ninja succeed in briefly freeing Zane from the virus' influence, allowing them to continue working at the Ninjigma puzzle in an effort to save him. The next portion of the Ninjigma proves to involve Garmadon, with different symbols representing aspects of both his Evil Lord and Good Sensei aspects. Eventually, they realize that only one image unites the two sides of Garmadon's nature: the image of the Green Ninja, his son Lloyd, which then proves to be the center of the final puzzle.
Prophecy of the Green Ninja
The Ninja attempt to decipher a maze of text about the Green Ninja, and find themselves forced to break down walls consisting of their individual elements. Memories of reaching their true potential prove to be the key, and they eventually determine that it will take the entirety of the team to solve the puzzle. This involves Nya digitizing memories of her own moment of true potential, as well as bringing Lloyd's mind into the computer as well. Unfortunately, their success unleashes an unexpected horror: it releases the Overlord, who has apparently been imprisoned in Lloyd's mind.
Nya determines that this Overlord Virus is a mere remnant of the Overlord from Zane's final battle with him, having been locked away by Zane's own security programming only to grow powerful enough to start affecting his systems. However, with the enemy revealed, Nya is able to use the memories of the Ninja and their previous battles to fight against the invader.