The Earth did not end in nuclear fire. The Earth did not end in nuclear winter. The Earth did not end in an ice age. The Earth did not end in global warming. The Earth ended in Darkness. The Dark Web claimed the Earth, and the modern world died.
As the Earth fell into Eternal Darkness, all the dead rose from their graves. Humanity changed from the predators to the prey. In a single day, the nations of the Earth were overturned, and the world fell into chaos and violence. Everyone that died rose again to kill more of the living, but not everyone who was bitten by the living dead died and become one. There were also those who Changed when bitten. The Changed developed powers that set them apart from humanity, and most of them sought to rule over the other survivors. The dead were hungry predators that ate the living, but were the real monsters the dead or the living?
When the Dark Web came, Walker Daniels was serving life in prison for the murders of the gang members that raped and murdered his wife. He was violent man, with only two men he considered his friends. In an attack by the newly risen dead, one of Walker's friends died, and he became one of the Changed.