"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.