The Great Old Ones consists of a set of six scenarios for Call of Cthulhu: The Spawn is in the Wild West, with Indians, Wobblies, and bad guys; Still Waters is an adventure for people who hate to lend books; Tell Me, Have You Seen the Yellow Sign? makes a symbolic stop-over in New Orleans; One In Darkness features South Boston hoodlums; The Pale God introduces investigators to an unusual contract; Bad Moon Rising is an experience to remember. The adventures can be presented in sequence, as a loose campaign; limited cross-references allow the scenarios to stand independently.