Cain, a disillusioned military scientist, believes humanity has failed to build a livable world. He sees extreme inequality, with a privileged few prospering while most struggle for survival. Determined to end suffering, Cain plans to activate weapons of mass destruction to eliminate all humans. Years later, he emerges from his shelter to find a desolate Earth, the intended site of his own demise. However, he detects a mysterious signal indicating another person is alive. He then sets out to find and eliminate this last survivor, completing his deadly mission.