In 2242, the returning deep space exploration ship "Prometheus" brought a terrifying parasitic virus called "Echo", which transformed the dead into extremely aggressive monsters. Ling Feng, a former special soldier who is now a prosthetic repairman in the quarantined city "New Green City", must go to the medical technology building occupied by "Echo" in the center of the city to find the only special medicine in order to save his sister who is suffering from "grey rot". He will rely on his extraordinary fighting skills and modified prosthetics to fight his way through the doomsday city, and gradually uncover the shocking conspiracy hidden behind the virus outbreak.
