What falls from the sky isn't rain, but man-eating snails. The apocalypse quietly descends. Qi Xu, a poor college student, struggles to survive in this post-apocalyptic world. He's calculating, sharp-tongued, and a master strategist. He claims to have a little conscience, but not much. Stockpiling food, fighting ruthless enemies, and fleeing alongside his companions, he gradually uncovers the truth behind the mutations of parasitically infected people. Beneath the surface of the shelter, dark currents are stirring. As Season One reaches its finale, a new crisis is only just beginning.