A strange, flying metal caravan lands on the Clangers' planet. It turns out to be a travelling shop, and its owner is a robot salesman. He has things he thinks the Clangers will like, and he's right - they do. However, they don't realise at first that the salesman wants to be paid. And when they do, they of course don't have any money. The dilemma is resolved when the robot spots the one thing he would really like in return. Unfortunately, though, that thing turns out to be Tiny's precious radio hat!