A friend of Leo Saint-Clair, Jacques d'Hermont, calls for his help because he and his family are slowly dying from of a mysterious disease. The Nyctalope investigates and discovers a new, deadly foe: Armand Logreux d'Albury, the so-called "Master of the Seven Lights," lurking in the Castle of The Cross of Blood...
Six years later, the Nyctalope crosses paths again with Logreux d'Albury and another of his arch-enemies, Engineer Korrid...