It is 1847, and Paris is edging closer to its next revolution, but something is also astir inside Mont Dragon in the Ardèche. This is a place of annual pilgrimage for a band of enigmatic nomads, and also a place of interest to the ambitious Bishop of Viviers. In spite of his distaste for travel, Auguste Dupin makes the long southward journey, in the hope that he might be able to help an old friend, the evolutionist Claude Guérande. Guérande believes that he has made discoveries in the caves of Mont Dragon that might cast new light on the origin of humankind, and of life itself. Over the years, however, not everyone who has gone into the caves has come out again, and not everyone who has come out has been unaltered... 1847 promises to be a critical year, more dangerous than any before it. And when the bizarre flameflower begins to bloom, everything changes! Another great tale in the Auguste Dupin series.