The key was almost stolen by the evil sorceress, Mamanu until Princess Lani tried to stop her. the key fell into the sea and was washed up on the shores of Enchancia where Sofia found it. The Royal Family return home with the key and look up the Emerald Key in the book The Complete Guide to Magical Jewels. They are visited by Princess Lani, who claims herself the owner of the Emerald Key. However, Mamanu disguised as Lani, claims to be the owner of the key. To determine who the real Princess is, the Royal Family put the two of them on some tests.
Mamanu cheated on the last test by making Lani's bed lumpy to get Lani to not get any sleep and fail, and Mamanu and gains possession of the Key. But Lani and the Royal Family realize that her bed is lumpy because Mamanu put her magic ring under the mattress to make the bed lumpy, so Lani wouldn't sleep well. Realizing that Mamanu had cheated, the family (except Sofia, who already knew) found out that Lani was the real Princess. When the Royal Family catch up with Mamanu, she revealed her true identity and tried to get away. But the animals in the forest stopped her, and Lani got the key back.
The Emerald Key gets returned to its rightful owners and leads the Royal Family of Hakalo back to their Kingdom.