One dark and stormy night, a sinister figure arrives in the little Gaulish village. Prolix, who claims to be a soothsayer, prophesies that when the storm is over the weather will improve. And it does! Now the credulous villagers believe every word he says, but Asterix has his suspicions of the smooth-talking Prolix. Who is really right about the soothsayer?
Julius Caesar sends Caius Preposterus, a bright young graduate of the Latin School of Economics, to corrupt the indomitable Gauls by introducing them to big business. Obelix's menhir trade is soon thriving, backed by a heavy advertising campaign - but does wealth bring happiness? And what will happen when the bottom falls out of the menhir market?