In the wake of Overlord's defeat, Ninjago City is reborn and the ninjas teach at Sensei Wu's academy. But the peace doesn't last long.

After being pursued to Sensei Garmadon's monastery by the Nindroids, the ninjas sneak back into Ninjago City under the guise of a circus train.

Zane gives up half his power to save P.I.X.A.L. just as foes attack from all sides. Meanwhile, Lloyd and his father travel to Hiroshi's Labyrinth.

Underneath Ninjago City, the ninjas discover secrets about the Serpentine when they fight alongside them against the Nindroids.

The ninjas venture into the Digiverse to confront the Digital Overlord. Meanwhile, Pythor and Wu lead a Nindroid attack on Borg Tower.

Pythor and the Nindroids free the Digital Overlord. Meanwhile, Wu and Garmadon stumble upon Pythor's top-secret scheme, Project Arcturus.

After battling Nindroids on the outside of the Arcturus ship, the ninjas hang on as the craft takes the battle into the heart of a comet.