The ninja are invited to attend the birthday party of Princess Vania in the Kingdom of Shintaro. They bring along Master Wu who is feeling his age.

Princess Vania reveals a secret entrance that leads to an underground mine beneath Shintaro where the city's dark secrets are held.

The ninja attempt to rescue Cole, but the bickering of his fellow prisoners alerts the Skull Sorcerer, and soon the ninja are prisoners too.

In order to escape the Skull Sorcerer's chain-gang, the ninja must convince the Munce and Geckles to put aside their distrust and work together.

Having become separated from the others, Nya, Jay and Lloyd are led back to the Munce "Home-Cave" by a Munce named Murt.

Kai and Zane stumble into a party of Geckels who think they may be working for the Skull Sorcerer.

Cole runs first into a nest of Dire-Bats, and then into a cave tunnel filled with giant spiders but Princess Vania and her pet dragon, Chompy, arrive just in time to free Cole.

Princess Vania attempts to catch the falling Master Wu and Cole, but their combined weight tears her wings loose. All 3 friends find themselves plunging into the mountain.

Cole awakens from a dream to find himself surrounded by the Lowly, Master Wu and Princess Vania.

Cole leads the Lowly, Princess Vania and Master Wu in a series of fruitless efforts to find a way out of the inescapable Rock-Bottom.

Nya uses her elemental powers to coerce the Munce into agreeing to a truce meeting with the Geckles.

Cole, Princess Vania, Master Wu and the Lowly arrive at an ancient abandoned temple. Wu realizes it is The Heart Of the Mountain.

The Skull Sorcerer hunts down the ninja who flee to the Geckle "Strong-Cave". The Skull Sorcerer promises to let the Munce and Geckles live if they turn over the ninja.

Cole, the Lowly, Princess Vania and Wu learn that the stone-mech is powered by Elemental Earth energy and use it to blast their way out of the mountain.

Cole and the Upply arrive at the Skull Sorcerer's Keep and find the ninja locked into cages. The Geckles and Munce have been put back to work in the chain-gang, mining Vengestone.

As Cole and the Skull Sorcerer face off, the Geckles and Munce storm the Keep. Plundar frees the ninja from their cages and the ninja join the battle.