From the introduction: This adventure is set in the 1990s, but (with suitable modification) it can be set in other times, such as the 1920s. The adventure takes the investigators into an area of New Mexico that has been plagued with a mysterious “hum.” It is up to the investigators to find the source of the hum and bring peace and quit back to the area. This adventure makes some references to “Blood Moon”, in Chaosium’s Strange Eons. However, knowledge of that adventure is not required to run this one.