Lui eats a dangerous berry, despite Plop's warning, and grows as tall as a human. The gnomes get angry, so Lui runs away crying and gets lost in the forest. Before he knows it, he ends up in the city, causing chaos wherever he comes..

One day Karen, Kristel and Kathleen receive an invitation from a king and queen from a distant fairytale kingdom. They ask if they want to sing on their daughter's birthday. But the princess behaves like a spoiled brat, because an evil wizard placed a curse on her, freezing her heart in the process. In an exciting race against time, K3 try to solve the mystery surrounding the little princess. But this turns out not to be as easy as they thought. Because even though they encounter all kinds of well-known fairytale characters, they do not receive any help. Will the brave singers manage to lift the curse?