from the introduction:
Gotham Legion is a Call of Cthulhu adventure taking place in New York City just before and during the heat wave of 1896.
The 10-day-long heat wave is a historical event responsible for the deaths of over 1,300 people. This adventure posits a Lovecraftian explanation for the heat wave – and for some of those deaths.
This scenario is available as a free download from Yog-sothoth.com (registration required)