Billy Webb is a young boy who likes to swap things with his school mates. He meets Alfonso Bonzo, an "Italian exchange student" who also has a talent for swapping things (thus his self-description: he is an Italian student who exchanges things). Alfonso offers Billy a variety of temporary swaps to demonstrate his abilities: Billy's boring old dog for a greyhound that does ballet, the wonky Webb family television for a new model with a button that lets the viewer become part of the action, Billy's battered schoolbag full of unfinished homework for a brand new schoolbag containing a file folder that magically produces finished homework... but each swap has disadvantages as well as advantages, and Alfonso Bonzo cuts an increasingly sinister figure as he leads up to one last swap, this one for keeps. The TV series later had a spinoff called Billy Webb's Amazing Stories, featuring Billy's further (non-Alfonso-related) adventures.