This is a tricky little investigation designed for 2+ characters. The specific setting can be anywhere in the continental US, so the GM is encouraged to create detailed maps and other props to assist players in visualizing the adventure.
BPI: If the characters are agents of the BPI or Sedgewick Society investigators, they may be called in due to the strange nature of the deaths.
Hired: The characters may have been brought in by McCloughlin Testing Laboratories, the police, or the family of one of the victims.
Curiosity: The characters may read details about the sightings and decide to investigate.