From the introduction:
This is a scenario intended for the 7th edition of Call of Cthulhu. It is assumed that you, the person reading this document, are the Keeper for this scenario. This scenario is set on June 14, 2019 in Milwaukee, Wisconsin in a fictional mall over the course of, at most, a day.
A freak blizzard hits the city of Milwaukee and forces people, including the investigators, into the mall to seek refuge from the storm. Proceeding the blizzard is a group of followers of The Great Walking White, intent on pacifying the people in the mall to seize a text they believe will allow them to commune with the Old One.
The investigators will have to find out what the cultists are doing, how to stop or hinder them, and survive the time they are trapped in the mall to make it through the scenario. Feel free to manipulate challenge rolls or create new ones that focus on different prominent skills some investigators may have.