In 1809, on a malign and gloomy Indian Ocean, the slave galleon Sulfuro is inexplicably destroyed by fire. 60 years later, British trading vessel the Bhangarh disappears without trace in the same location. Only one crewmember from each tragedy survives to warn the world of the terrifying events that transpired. But their depositions are lost upon an apathetic public and soon fade into the mists of history. It is only in 1936 when Nazi Germany takes an interest in the Sulfuro Bhangarh manuscripts, that occult anthropologist Richard Marsh decides to investigate. By piecing together the disparate threads of the story he begins to unearth evidence of a dark and ancient conspiracy whose ultimate aim is nothing less than the end of civilisation.