Cain, a disillusioned military scientist, has lost faith in humanity. He believes that people have failed to build a world worth living in, where only a select few enjoy prosperity while the majority endure suffering and a relentless fight for survival. Driven by this belief, Cain decides to eradicate the human race by deploying weapons of mass destruction. After some time, he emerges from his shelter, seeking a place to meet his end as the last human. However, he unexpectedly picks up a mysterious signal suggesting another person is still alive. Determined to finish his mission, Cain sets out to find and eliminate this survivor.