Mia and Paula are working on their schoolwork, but are having trouble concentrating with loud music playing in one of the other nearby rooms. Needing a quiet place to study, Mia asks Vincent if she and Paula can use the shed. Vincent is reluctant, since the place has been his and Mia's secret place up until now. Mia eventually convinces him to allow Paula inside, and she is amazed that no one else has discovered Vincent's secret hideout. Vincent still feels a bit awkward about having Paula there, but tries his best to accept the situation. Mia and Paula are able to study, but Vincent still isn't sure how to feel about the situation, accidentally causing some disturbances in the background. When Mia's bracelet starts glowing, Vincent has to keep Paula company while Mia heads to Centopia.
Mia arrives in Centopia and greets her friends. She quickly learns that something is wrong with the water barrier. Mia tells them about the newest riddle, and they quickly reach the conclusion that it refers to Polytheus' island. The group arrive at his island, and want to look for it without being seen. Mia suggests that they could just try asking him for it, but the others point out that he would refuse to give it to them for free once he knows it's worth something to them. Mia accidentally comes across Polytheus, who wonders why they're intruding. The group try to figure something out, suggesting that they might be interested in buying something and distract Polytheus so Mo can enter the cave.
Mia tries to keep Polytheus' attention while Mo searches the treasure hoard for the trumptus piece. Mia compliments a fountain in his hideout, and Polytheus brags about his skill with water. Onchao eventually locates the trumptus piece, but Polytheus discovers Mo sneaking around. To keep out of trouble, the fairies claim that King Raynor wants to reward him for having helped out the elves a few times before, and that there will be a ceremony and a banquet at the castle. Polytheus has to give something to Raynor, and they suggest he gives the trumptus piece, since Polytheus doesn't know what it is.
As Mia escorts Polytheus while Mo and Yuko fly ahead to the castle, Mia comments on how Panthea's actions have left much of the area barren, leaving little food for his giant turtle. Yuko and Mo arrive at the castle and explain the situation to King Raynor, and they begin working on trying to put something together before Polytheus arrives. Polytheus tries to find something for his turtle to eat, and Mia questions how Polytheus can ignore what Panthea is doing to Centopia. Mia eventually uses some unicorn dust to revive a plant for the giant turtle to eat.
Elsewhere, Panthea and some other dark elves spot Onchao near the castle, and noting that the water barrier isn't working, prepare to attack. Yuko and Mo look around at their hastily prepared ceremony, as Polytheus and Mia arrive. Polytheus is not impressed, and Mia suggests they hurry up and make the trade since Polytheus won't believe their act for long. Polytheus realizes that they're up to something, and wonder just what the whole act was about, curiously examining the trumptus piece. The elves spot the dark elves flying towards them, with King Raynor mentioning the water barrier still being broken. Polytheus is about to leave, when Mia asks him to hand over the trumptus piece, telling him that they need it to stop Panthea from turning more of Centopia into a wasteland.
Polytheus thinks about it for a moment, and decides to go do "what he does best", as Mia flies off to assist her friends in fighting the dark elves. Raynor and Mayla join the fight, but the elves' water shooters are running low on water. Suddenly, the water barrier activates, forcing the dark elves to retreat. Mia looks around for Onchao, and asks Polytheus if he did something. She soon realizes that Polytheus repaired the water barrier, and he leaves the trumptus piece behind on the ground, pretending to have dropped it without noticing. Onchao restores the trumptus piece, and Mia comments that Polytheus is probably on their side now, before heading home.
Returning to her own world, Mia goes to check on Vincent and Paula, and finds that the two of them are getting along just fine.
- Neutral No Longer: Up until this episode, Polytheus had been the Wild Card in episodes involving him, assisting either the heroes or the villains if they had something of value to him. Other than that, he doesn't get involved much in the conflict between the elves and Panthea. By the end of this episode, he's on the elves' side for the remainder of the season.