The school is having auditions for a talent show, and Mia demonstrates her tap dancing skills. Violetta comments that while she is sure her singing is better than Mia's dancing, it'd be better if Mia didn't participate. Later, Mia asks Paula what she plans to do for the show, but Paula doesn't really have any plans aside from assisting Violetta, since Violetta says she is sure to win anyways. Mia then asks Paula if she'd be interested in tap dancing, and shows her how. At the talent show, Mia notices that her tap dancing shoes are missing. Vincent decides to try to come up with a substitute using Mia's regular shoes. Mia's bracelet glows, and Mia heads to Centopia while Vincent works on the shoes.
Arriving in Centopia, Mia finds that Onchao seems anxious about going somewhere. Raynor notes that other unicorns seem to be headed towards a volcano, and wonders if the Fire Unicorn has something to do with what is going on. Yuko and Mo tag along as well, and wonder if a trumptus piece might be somewhere near the volcano. The elves soon learn that there's a ceremony going on where the young unicorns are accepted into the herd. The elves are told by the older unicorns that they can't follow Onchao inside, but they decide to sneak in anyways since there might be a trumptus piece somewhere inside.
Elsewhere, Panthea is annoyed by all the smoke coming out of the volcano, and sends Gargona to try to do something about it. Inside the volcano, the elves secretly follow the young unicorns, watching from a distance. Mo initially wants to ask Onchao to look for the trumptus piece, but Mia doesn't want to disrupt the ceremony, so Mo and Yuko decide to look around on their own. It doesn't take long for them to spot it, but reaching it is easier said than done. Soon, the Fire Unicorn appears. A ball of fire ends up carrying the trumptus piece out of the volcano, and Yuko and Mo head out to try to retrieve it while Mia stays behind.
The Fire Unicorn creates a ring of fire between the cliff it is standing on, and the cliff the young unicorns are gathered on. The young unicorns must jump through the ring to the other side. Outside, Yuko manages to find out where the trumptus piece landed, however, shortly after grabbing it, she and Mo get trapped under a fallen tree. As if that wasn't bad enough, Gargona and some dark elves are approaching on dragons. Back inside the volcano, it is Onchao's turn to jump through the ring of fire, when Mia's friendship ring alerts her to Yuko and Mo being in trouble. The Fire Unicorn spots Mia, and she quickly excuses herself and tells Onchao to finish the ceremony. However, when Mia nearly falls, Onchao ends up flying to her aid. The Fire Unicorn observes from a distance as the two fly off to help their friends.
Mia shows up, just as Gargona and the dark elves reach Yuko and Mo's location. Mia's tap dancing skills allow them to move the log, and the battle continues. Mia manages to hit Gargona with her water shooter, and the now shrunken Gargona calls for her troops to retreat. The group head back to the volcano, but the Fire Unicorn appears to have left. Mia tries to cheer up Onchao, but the Fire Unicorn soon returns and reveals that he was impressed enough with Onchao's courage to give him a second chance. Onchao must jump through the ring of fire without using his wings, and manages to barely make it across successfully. Satisfied with Onchao's performance, the Fire Unicorn leaves.
Onchao is now officially part of the unicorn herd, and restores the trumptus piece to its shiny appearance. Mia heads back to her own world, just in time for her performance at the show. Vincent shows up with his improvised attempt to provide Mia with a replacement for her tap dancing shoes, when Paula shows up and reveals that she found Mia's tap dancing shoes. Mia invites Paula to dance with her in the show, and the two perform together.
- Four-Element Ensemble: As the episode title implies, this episode introduces the last of the four elemental unicorns, the Fire Unicorn.
- Initiation Ceremony: Young unicorns are officially accepted into the herd after the ceremony with the Fire Unicorn.
- Tempting Fate: When Yuko and Mo get stuck under a fallen tree, Mo wonders out loud what else could possibly go wrong. Yuko calls Mo out on this when Gargona shows up right afterwards.