Mia has a new adventure in Centopia when Lyria's new baby unicorn, Kyara, is born. Mia discovers Onchao has new powers. Onchao saves Lyria and Kyara from the Grotto with his new powers. Mia finds another friend in the real world - Sara.
Mia and Sara want to surprise Sara's mom and clean up the house, to convince her that Peppino can stay at the Poletti stable. While preparing salad and pasta, Luciana arrives with Mr. Monti. In Centopia, King Raynor and Mayla fall into a coma due to the evil powers of the Night Vine. Mia and her friends have to find a way to defeat the plant.
Synopsis: Mia and Sara have slept in their sleeping bags in the hayloft and Mia is introduced to all the animals at the Poletti farm, when her bracelet summons her to Centopia. There Mia and her friends head out to meet the Pan King who is said to own a similar crystal that could be a part of the "Heart of Centopia".
Mia and Sara are milking the goats when the postman delivers a letter from Sara's school, which makes Sara feel uncomfortable. In Centopia, Mia finds out that Yuko has a sister named Kuki who lives in Flowerdale Village. The friends go there to find the next Heart Crystal.
Mia meets Fabio who is harvesting his bees, while Sara is picking raspberries, and she notices that both have some history together. Onchao has a boys-day-out with Esko, while Kyara leaves the Elven Crater unnoticed. The Elves try to find her back, but Dax and the Hoppers are always one step ahead. Kyara gets lost in the forest, where she finds Lavera and her unicorn Kindergarten group.
Mia and Sara are cleaning up a room in the farmhouse, when Mia finds an old ghetto-blaster and a box of trophies which obviously belonged to Sara. She reveals to Mia that she used to do Hip-Hop dancing before the accident. When Phuddle destroys his laboratory inside the Elven Crater, King Mo harshly forbids him to rebuild it inside the Crater.
Luciana finds the letter from Sara's school and issues an ultimatum to Sara. The school wants her back and she needs to decide if she goes to a special school in Milano or her old one. In Centopia, Mia and the Elves could get a Heart Crystal from Polytheus, but only in exchange for the most precious thing they can find.
After tourists report that they have seen a wolf in the mountains, Mia and Sara set out on Peppino to search for the wild animal. In Centopia, Mia, Yuko and Onchao fly to the dragon caves in search for a Heart Crystal. But the Night Vine has already covered most cave entries. They have to help Baby Blue to find a lost dragon egg before night falls.
Fabio tries to make Sara dancing again, and leads her to his slack line where they do some balance training. Meanwhile Mia travels to Centopia and has to witness a rather sad event. Together with the Elves and Kyara she travels to a mystic hill called the Seventh Wave where they meet Landa, Kyara's grandmother.
In order to help Suzanna the goat with her colic, Sara and Mia hike into the mountains to search for mountain avens, when Mia reveals her secret to Sara. But she doesn't take Mia's words very seriously. In Centopia, Mia and Mo learn about Yuko's secret hobby: she trains her singing skills.
Mr. Monti is teaching Fabio how to ride, when Mia and Sara show up. But soon Mia has to leave for Centopia. The oracle tells the friends to find Simo and Lasita. They send out a friendship butterfly that leads them over the ocean. But after a storm they crash-land the balloon throne and get trapped on an island with Ponycorns
A fox has broken into the chicken coop, so Mia and Sara try to fix it before the fox comes back catching another chicken. In Centopia, Mia and the Elves visit their friends at Blackwood Forest where the oracle tells them to look for a Heart Crystal. Simo is able to decipher it and knows where to go: to a field of electrifying snoot-blossoms.
It is Mia's birthday, so Sara and Luciana surprise her with a little birthday cake. Later, the girls are hiking in the mountains. When arriving in Centopia, Mia is right in Flowerdale and just in time for the Lunar Festival. But Kuki doesn't believe that the ballad of the Moon Unicorn is true.
Mr. Meloni is presenting a brand-new BCS (Braille Computer System) to a rather reluctant Sara in order to convince her of coming back to school. In Centopia, Yuko has discovered a strange insect cocoon from which a giant butterfly hatches. According to the oracle, Mia and her friends plan to follow the butterfly to where it wants to fly.
Mia and Sara are preparing handmade pasta for today's dinner and Mia is still trying to make Sara believe in Centopia. Whereas in Centopia Gargona and Dax try to distract Lord Drakon with a little Bluebardo. At the same time Mia and her friends get unexpected visitors.
A real estate agent shows up, wanting to buy land from Luciana. She will need the money to send Sara to a specialised school. While Sara is saddened, retreating to her room, Mia travels to Centopia. The oracle leads Mia and her friends to Flowerdale and the swamp, where they meet the Elven girl Lola.
Mia and Sara are having a picnic and then decide to go to the village for some ice cream, also for training Sara's skills finding her way in crowded places. But Centopia summons Mia and there she witnesses Mo honoring Yuko with the official Unicorn Guard Award, which he just invented.
While hiking, Mia and Sara are surprised by a thunderstorm and find shelter in an abandoned cabin. Mia teaches Sara some more Elven runes when her bracelet starts blinking. In Centopia, the Night Vine has taken over many parts of the island and the Elves still need to collect more Heart Crystals in order to stop Dax and Lord Drakon.
Sara would love to travel to Centopia as well. When Mia gives her the bracelet, it suddenly starts blinking and Mia wants it back. The girls hassle about the bracelet, it falls down and a piece of the magic stone breaks away. But still, Mia can travel to Centopia and gather her friends to fly to the Crystal Cave in order to get the next Heart Crystal.
Mia tells Sara about what she has seen in the crystal mirror in the Crystal Cave in Centopia - meaning Sara will also travel there somehow. But not this time yet. Mia visits Centopia alone again, appearing right in the middle of the Flowerdale Elves' exodus into the Elven Crater. The Night Vine has overrun their home.
After Mia apparently didn't return from Centopia, Sara is desperately searching for her. But when Wolfie finds the bracelet, Sara gives it a try and... travels to Centopia. When seeing that Sara wears Mia's bracelet, they doubt she is a friend. But she can convince them that they all need to help Mia now, being held hostage by Dax and Gargona
Sara needs to make up her mind about school. Mr. Meloni and Fabio, who finally learned to ride on horseback, try to help her with her decision. But Centopia calls in the middle of their meeting, so Mia and Sara retreat and travel to Centopia hand in hand. Yuko and Mo are still trying in vain to assemble the crystals to the Heart of Centopia.