The Big Dark Sky By Dean Koontz

Joanna Chase's tranquil life in Santa Fe is disrupted when she starts receiving mysterious pleas for help from a dark place, urging her to return to Rustling Willows Ranch in Montana, where she grew up. Despite having hazy memories of her childhood there, Joanna feels compelled to answer the call.

Upon her return, Joanna discovers that she's not alone in her journey. A diverse group of individuals with their own troubled pasts has also been drawn to the ranch, each grappling with their own demons and seeking answers to the same ominous danger that Joanna is facing.

As they navigate the remote ranch and its surroundings, they realize that a deranged individual harbors a sinister plan to enact mass murder in order to fulfill a terrifying vision for the future.

With their lives intertwined and facing a common threat, Joanna and the others must band together to confront the encroaching horror and prevent the madman's catastrophic plan from coming to fruition. Under Montana's expansive sky, they must confront their fears and unravel the mystery before it's too late—for themselves and for humanity as a whole.