Robert D. Anderson, a New York private investigator and last descendant of an old aristocratic family, becomes involved in a mysterious case that leads him to investigate his family's past and a connection to the occult. His investigation takes him to Germany during the era of the Third Reich, where he becomes entangled with the secretive Order of the Black Sun and its supernatural activities. The story unfolds across 15 chapters combining investigation, exploration, puzzles, combat, filmed sequences, and Lovecraftian horror.