Call of Cthulhu RPG: Spawn of Azathoth (1920s)
Astronomers have theorized our sun is not alone in its journey around the galaxy, but is accompanied by an unknown second star of dim radiance. This second star, while perhaps invisible from Earth even with the finest optics, would periodically pass close enough to solar system to have far-reaching effects upon the evolution of this planet.
Spawn of Azathoth is a campaign supplement for Call of Cthulhu. The adventure begins when an investigator is awakened by a ghostly apparition. Soon the investigator and his friends are drawn into horrifying events, luring them across the United States, overseas to the Andaman Islands and to the interior of Tibet, and to places even further beyond. Gradually they come to understand the dread fate toward which the Earth hurtles, a fate which only they can avert. (from the back cover)
Spawn of Azathoth is a 200 page soft cover, perfect bound book with black and white illustrations. There are 26 pages of handouts for the adventures at the back of the book.