Eden of the substitute

Luo Ran has been investigating the death of his wife with his best friend Ning Yu. They end up getting onto a train headed for C City in order to chase female suspect Jiang Xue. The train suddenly derails mid-journey, and the hundred or so survivors find themselves transported to a ruined city with no living soul in sight, cut off from the rest of the world. The city is filled with dangers on all sides and supplies are dwindling. The survivors start dying off or disappearing one by one—a brutal game of survival begins.

After the death of her policeman father, Xiaomai begins to look over his old journals filled with notes about the cases he investigated over the years. The mention of a purple scarf in the notes particularly catches her attention, prompting her to purchase a similar scarf from a mysterious website that claims to sell everything, as long as one can pay the price. Soon after, Xiaomai's close friend is found dead, strangled by a purple scarf. All of this awakens Xiaomai's memories of her childhood sweetheart Qiushou, whose mother was also strangled to death with a purple scarf by an unknown killer. Xiaomai and Qiushou grew up together and fell in love, but he suddenly disappeared from her life 15 years ago without a word. She begins to believe that Qiushou has returned and may be seeking revenge.