Gravity is no longer just a force of nature—it's a weapon.

When a professional BASE jumper is found dead at the base of an unfinished San Francisco skyscraper, strapped into a sabotaged rig filled with lead shot, Detective Sarah Jenkins and FBI Special Agent Thomas face a chilling new kind of homicide. There are no signs of a struggle or a forced entry—only a precise, yellow mathematical equation scrawled on a steel girder high above.

The killer is a master of gravitational physics, turning the city's vertical architecture into a lethal chalkboard. As high-rise elevators and coastal transit systems become high-altitude execution sites, Jenkins and Thomas realize they are hunting a calculating mastermind who is testing drop weights and calibrating terminal velocity.

Nursing a painful, severe arm injury from a previous case, Jenkins must push her body to its absolute limits. Alongside the immovable and analytical Agent Thomas, she races against a terrifyingly precise countdown to stop a killer who is proving that gravity never misses its mark.