A love story told in letters that are exchanged by an anonymous public artist and an admirer who wants to know the man behind the murals.

In a series of interviews with the KND after they're all grown up, the former operatives are temporarily brought out of their decommissioned haze to discuss what happened during their very last mission with Numbuh one - where he disappeared and was never heard from again! It all started with a routine mission to get the Delightful Children's birthday cake, but when a mysterious boy steals it instead, he makes it available to whoever wants it, IF they can solve his 'simple' scavenger hunt first. Soon it's a mad, mad, mad, mad chase around the world as the KND, their friends, and virtually all of their enemies compete to win the yummiest cake ever