So this story idea concerns a sweets shop in a small village in Switzerland or somewhere else European and slightly medieval. The shop produces excellent sweets and candies of all kinds, and is a favorite of children for miles around, not only because it sells good things to eat, but because the sweets are magic. Each candy, depending on its type, bestows a kind of magical power on the child who eats it. Swedish fish, for example, allow a child to breathe underwater for about an hour or so after eating one. Lollipops, when successfully licked, grow larger rather than smaller, until they reach the size of a large balloon, whereupon, if the child holds tight to the stick, he is lifted up into the air where he floats around for an hour or so until the balloon pops and he is let down.
Each year, the candy maker creates a new sweet, and the children who know about the shop line up for blocks to try it out. But one year, the new item--peppermint sticks--go dreadfully wrong. The sticks make the child who eats them invisible, just as planned. Unfortunately, the effect does not wear off after an hour or so. Furthermore, not only can the children not be seen by their parents or others who have not eaten the candy, they cannot be heard either. In trying to make their parents understand what has happened to them, they only succeed in spreading the rumor that ghosts have descended upon the little town.
Finally, the children approach the candy maker, who is, after all, a sort of magician. They write him a letter and he dusts them with confectioner's sugar so that he can see if they are telling the truth. When he consults his recipe book for an antidote, he finds the recipe for a stick of chewing gum that will make the children visible again. The ingredients in the recipe, however, would take years for him to collect, for they are nearly all difficult to find and in remote areas of the globe. The children decide to divide into groups and assign a different ingredient to each group. They scatter across the globe in search of the item on their lists, encountering all sorts of adventures along the way. The details of their adventures comprises the subsequent books of the series, which end only with the last one in which the children finally come together to create the gum that will render them visible again.