Without warning, a jetliner falls from the clear blue sky ahead of a startled motorist, who manages to capture the last few seconds of the doomed flight on his cell phone. As frightening as the video is, none of the horrified viewers watching it play out on newscasts across the globe that evening understand its true significance. The last sane day on planet Earth is already behind them. And it will only get worse. The day before, John Cruz had awakened to find himself in unfamiliar surroundings. He learns that he's been in a mental hospital for nearly three years - confined there for a crime he does not remember, a crime the hospital staff refuses to discuss with him. But soon he discovers something even more bizarre. While he and other mental patients like him are mysteriously recovering, the rest of the world is beginning a descent into madness, thanks to a mysterious disease that causes many of its victims to go violently insane. Meanwhile, overhead, a spectacular apparition splits the skies, as the largest comet in recorded history makes a close approach to planet Earth. Some scientists believe that not only is the comet somehow connected to the spreading madness, but that this has happened at least once before in human history, with apocalyptic consequences. As events close in, John will have only one task, and one question: will his mind slip away again before he can save the love of his life from the growing chaos?