Marianne and Ben are terrified to discover they are the victims, like most of the population, of a very serious and inexplicable intoxication. Only the ten surfers seem to have been mysteriously spared. The city is quarantined by the authorities. The life of the Brizannais is now at stake; they realise only too late that Ben and Faust Ketchak were right and all make the connection with the cloud that has infiltrated the city the previous night. Mad with worry, Ben continues to search for answers. He discovers that the solution could come from the surfers themselves.