Mia and Sara are on a walk with Peppino, when they come across a guy howling like a wolf. Sara knows who it is and assures Mia he is harmless, before asking about why he's acting that way. He believes there might be wolves in the area, and is trying to find out whether it is true or not. As Mia and Sara are riding home, they hear something that sounds like an actual animal, and feeling it sounds like it might be hurt, go to investigate. As they get close to the source of the sound, Mia moves closer, discovering that the animal is just a dog that has gotten stuck in some rocks. The guy from earlier shows up again, and helps them rescue the dog. As they are bandaging the dog's paw, Mia's bracelet glows and she excuses herself for a moment.
Arriving in Centopia, Mia meets up with Shiva, who informs her that Yuko and Mo are busy cleaning up inside the castle. Mia ends up falling into one of the boxes inside the throne room, wondering why there's so much stuff in there. Mo explains that as the current king, it's tradition to go through these old things. Mo happens to find an old flute, used in the old times to summon the Sun Unicorn. Mia tells the group about the latest riddle, and Mo concludes that their next destination is the dragons' caves. Phuddle insists Mo can't leave, so Mia and Yuko head out on their own, with Mo entrusting Yuko and Mia with the flute and the heart shard for the mission.
Mia and Yuko travel to the dragons' cave, which has been partially covered by vines. They spot their old friend, Baby Blue, among the dragons, who is desperately trying to get into the cave to retrieve his eggs. One of the other dragons is poisoned by the thorns. Mia, Yuko and Onchao are small enough to get past the thorns partially blocking the entrance to the cave, and promise to help Baby Blue get his eggs to safety.
Back at the castle, Phuddle tries to cheer up Mo, who is bored with being stuck cleaning. Mia and Yuko realize it's getting dark, and worry they won't find the egg. Recalling the riddle, Mia wonders if they can use the flute to summon the Sun Unicorn. However, it turns out the mouth piece for the flute is missing. Yuko flies back to the castle to retrieve it, while Mia stays behind. However, Yuko struggles to fly fast enough to get back before the sun goes down, until Baby Blue catches up to her to give her a ride.
Mo has just finished cleaning up, when Yuko arrives riding on Baby Blue. Yuko explains the situation, and Mo prepares to head out. Phuddle checks the list to find out where the mouth piece for the flute is, only to find that Mo forgot to mark the box. However, Phuddle freaks out when he realizes he never did find the mouth piece, meaning their task isn't finished. Kyara enters the room, and uses her horn to locate the mouth piece.
Meanwhile, Mia and Onchao continue looking for Baby Blue's egg, and Onchao eventually helps Mia find it.
Yuko and Mo are riding Baby Blue back to the caves as the sun is going down. Mo plays the flute to try to summon the Sun Unicorn, but because the sun is already going down, Mo thinks it is already too late, since the Sun Unicorn can't be summoned at night, until he reasons there might still be some sun on the other side of the mountain. They fly higher, seeing a glimpse of the sun, and hurry over to reach it before its too late.
The plant is spreading to cover the cave entrance. Onchao manages to make it out before the thorns cover it completely, but Mia still trapped inside. Getting close to the cave with the sun still visible, Mo tries playing the flute again. Since nothing seems to be happening, Yuko wonders if it was perhaps just a myth, until the Sun Unicorn arrives from where the sun was going down. The Sun Unicorn makes the sun rise again, before using its power to make an opening in the thorns big enough for Mia to get out along with Baby Blue's egg. Mia gives Baby Blue his egg, and thanks the Sun Unicorn for helping them.
The elves witness Baby Blue's egg hatching, and comment that something good did come out of the day, even if the cave is now inaccessible and they still haven't found the heart shard. However, the heart shard Mo lent to Mia begins to glow, and Baby Blue reveals that he had the shard.
Mia returns to her own world, and asks how the dog is doing. The man responds it'll probably be okay, and since the dog is probably abandoned, they'll need to find a new home for it. Concerned for the dog, Sara decides to take it home herself and convinces her mother to let her keep it, naming it Wolfie.
