The Masks of Nyarlathotep

"At last the stars are almost right. Soon Nyarlathotep's plans will come to fruition. Then the world will be changed irrevocably - but not quite yet. Pesky human investigators have learned much. Now they must survive long enough to make sense of what they know, and take resolute action.
This roleplaying classic is a series of linked adventures forming one long and unforgettable campaign. Horrifying deeds and dangerous sorcery dog those who dare attempt to unravel the fate of the Carlyle Expedition. The non-linear narrative keeps players baffled and on their toes. Action is the byword as the player-characters evade or combat cultists, magic, mad men, and the dread powers of the Outer Gods."