In the post-apocalyptic future, humanity lives in artificial habitats that can meet all their survival needs.
Qi Huai works at one of these habitats. Every day, his job is to search Earth for any survivors and confine them in the "zoo."
A strange factor in the air affects normal humans, making them mutate and lose their humanity until they no longer recognize even their own families. Their intelligence surpasses that of ordinary zombies, and they move faster than cheetahs.
On one routine outing, Qi Huai gives in to his feelings.
That person looks so much like Qi Huai's dead older brother.
Qi Huai arranges for Fang Zhiyan to blend in with the "normal people." But one day, the secret gets out, and all the "animals" in the habitat escape. They attack every human indiscriminately, except Qi Huai.
The sun illuminates the city's ruins, and the sunset shatters across the horizon. Fang Zhiyan holds Qi Huai as they travel with the group back to their nest.
Dazed, Qi Huai asks Fang Zhiyan why he doesn't kill him.
Fang Zhiyan smiles. "That way, I can spend the rest of my life demanding revenge from you."
