Two scientists, Erin Gilbert and Abby Yates, after years of going their separate ways following their collaborative book on the paranormal, reunite when Gilbert seeks to disown the book as it threatens her tenure at Columbia University. Gilbert's academic ambitions are upended when she and Yates witness a real ghost, affirming their long-held beliefs. Along with nuclear engineer Jillian Holtzmann, who builds experimental equipment, they begin an investigation into a sudden surge of apparitions across New York City. They form a team dedicated to studying and stopping the ghostly phenomena.

As the sightings increase, the team hires Patty Tolan, a subway worker who encounters apparitions underground and brings local city knowledge to the group. Together, they uncover a nefarious plot by an occultist aiming to amplify paranormal activity in the city and bring about an apocalypse. Armed with their specialized equipment and a deepening understanding of the supernatural threats, they prepare to confront the growing paranormal menace.