1874: five years into the space race, Earth's major powers are colonizing the solar system. France and England dispute the sovereignty of Venus which (in keeping with the actual era's scientific beliefs) is a fog-covered jungle world where life is still in the primordial stage. There, operetta actress Hélène Martin is searching for her fiancé, poet Aurélien d’Hormont, an escapee of Napoleon III's labor camps . Pursued by the ominous Duke de Chouvigny and caught up in the rivalry between the two empires, Hélène must make her way through dinosaur-infested jungle and cross stormy oceans to the planet’s strangest frontiers, where the vestiges of a mysterious civilization await.