Gupi and his friends enter an empty apartment in their building to deliver a cake, but after passing through a wardrobe, they find themselves in a dark, gloomy, and unfamiliar dimension. This strange world is home to the palace of the Unsmiling King, whose sadness has spread throughout the land. Realizing that everyone in the realm has lost their joy because the king never smiles, the friends try various ways to make him laugh and bring happiness back to the kingdom.