Twelve years after the devastating eruption of the Krakatoa volcano in the strait between Java and Sumatra, the country still cannot find peace. A yellow fog rises from the depths of the earth, and at night eerie creatures appear from there. Strange horned creatures are terrifying the local population. The Governor General of the Dutch East India Company is concerned about the increasing number of attacks. He turns to his foreign minister, who, in turn, asks the director of the University of Berlin for help. The only person capable of revealing the secret of the stone devils from the island of Java is Karl Friedrich von Humboldt, an expert in unexplained phenomena and the leader of a team of fearless seekers.