When an unscrupulous shopkeeper settles a debt with Fantasio by offering him a mysterious 'gismo', the reporter has no idea how much trouble is following in the thing' wake. It turns out to be a sort of robot that soon takes our heroes on a made chase leading to Champignac- and an equally mysterious young woman sequestered in a cellar. And as if that wasn't enough, every electrical appliance in town seems to be going haywire...