Part 1: Numbuh 5 is kidnapped and sent to a temple to find a mystical flavor of ice-cream known as "The Fourth Flavor" for the DCFDTL. She dreams of having a chance to taste the long-lost flavor herself, for only those with pure taste buds may taste it. Part 2: Numbuh 2 is turned into a teenager when an experiment goes wrong, but gets smooth with Numbuh 5's older sister.