Za sprawą tajemniczych pamiątek, jakie pozostały po jej rodzicach, 12-letnia Mia poznaje zaczarowany świat elfów, jednorożców i złej królowej o imieniu Panthea.
When Mia comes back to Centopia, she finds that everything is peaceful and harmonious. The only problem is Phuddle inventing a lawn sprinkler that floods the whole palace with water.
Mia, Yuko, and Mo try to find proof that Rixel is playing a tricky game on them. While visiting his circus, they check out the backstage area, where they find animals held in captivity. Meanwhile, Onchao is captured by Gargona.
Mia is looking for Onchao, who is still fighting for acceptance amongst Esko's foal group. Rixel plans to get into the elven crater by waving the white flag.
Rixel and Gargona try to catch and hypnotize a dragon to use as air transport. The elves discover the plan and protect the dragons. But when the friends reach the dragon caves, the dragons see a danger in the elves.
Rixel destroys the pepper supplies in the Elven Crater, and Mia and co have to go into the mysterious black forest to replenish supplies. Raynor warns the Elves that a ghost protects the black forest.
With a device procured from Polytheus, Rixel manipulates the animals in the crater to make them show him the secret tunnel. Mia and her friends have to master the chaos that the hypnotized animals cause in the Elf Crater.
Following Rixel's last attack, Mia decides that she needs to find out more about the black oil. Phuddle wants to help, but placing the oil in his hands is too dangerous!
When Mia arrives in Centopia, she has to learn that Onchao is missing. He had an argument with his mother Lyria about his father Ono and wanted to look after him.
Mia, Yuko, and Mo leave for the Unicorn Meadow to pick up Onchao. Mia interprets the Oracle as telling them to go to the Windy Cliffs to start their search for the four Rings. They don't notice Gargona spying on them.
The Oracle tells our heroes they should look for the next ring in the stars. Simo shows them a spot in the forest where they can watch the stars, but the night sky is cloudy. Tessandra tells them to go into the desert instead.
An otter named Scrobbit steals one of the rings and escapes via the waterfall. Our heroes chase him to Polytheus' island, and Mia demands that the otter return the ring of Polytheus.
When Mia lands in the elven crater, she notices that today is the day when each elf has a gift for his best friend. Because no one has a present for Xolana, Mo gives her the one he actually had prepared for Yuko.
Mia meets Yuko and Mo at the Unicorn Meadow, where Onchao is playing with Esko and the other foals. Mia's Oracle indicates that the fourth Ring might be in Panthea's Palace.
The friends have assembled the four rings. They now have the key to the Rainbow Island, but where is the lock this key fits into? They have to decypher the runes engraved into the ring.
Together with Mia, Violetta arrives in Centopia. She calls herself Varia and claims to be a princess from another island who has lost her memory. When Varia learns that Mia plays a central role in Centopia, she becomes jealous.
From her oracle, Mia knows that Panthea is the only one who knows where Ono is. If the elves could bring one of those flowers Panthea dissolved into, Tessandra can try to "make the flower speak."
Mia and her friends plan to set off to the icy North Horn to find Ono, but Raynor tells them that they have to protect themselves against the cold. In Centopia's volcano, they find the unique fiery flower to help protect them.
Mia lands next to the igloo at the North Horn, where she left Centopia the last time. Mia, Yuko, Mo, and Onchao say farewell to the bluebardos and head off to the secret island.
Mia lands in the elven crater, where Ono visits the royals together with his son. Phuddle has a new invention as a gift for the returned king, which turns out to be disastrous - naturally.
The friends visit the Blackwood Forest, where Tessandra is starting her work on the potion to defeat Rixel, using the Rainbow Water the friends obtained. The friends play hide and seek together in the Blackwood Forest.
The elves plan a major attack on Rixel's island, but they have to trust each other. Mia suspects Varia to be Violetta. When Mia wants to confront Varia with her suspicion, Varia accidentally reveals her true identity.
Mia and her friends load their sprayers with rainbow water. They use it to break the spell on the Unicorn King. The use Rixol's Dragon (now their ally) to enter Rixol's island. They chase Rixol and Gargona from the island and Mia pours some rainbow into the evil green spirits cauldron turning the island into a island of flowers. Mia wins the horse events in her world and saves her grandfather's farm.