On the morning that marks the end of the world they have known, Molly and Neil Sloan awaken to the drumbeat of rain on their roof. A luminous silvery downpour is drenching their small California mountain town. It has haunted their sleep, invaded their dreams, and now, in the moody purple dawn, the young couple cannot shake the sense of something terribly wrong.

As the hours pass, Molly and Neil listen to disturbing news of extreme weather phenomena across the globe. By nightfall, their little town loses all contact with the outside world. A thick fog transforms the once-friendly village into a ghostly labyrinth. And soon the Sloans and their neighbors will be forced to draw on reserves of courage and humanity they never knew they had. For within the misty gloom they will encounter something that reveals in a shattering instant what is happening to their world--something that is hunting them with ruthless efficiency.