At the Eighteen Turns of Songpu Wharf, in the bitter cold, Erzi, a poor country boy, is beaten to the brink of death by the thug Bai Juntian. He is saved when the spirit of Wuyun Xiao, a cat immortal who has lived for a thousand years, possesses him. The two form a symbiotic pact, granting Erzi supernatural powers and transforming the timid boy completely.
Moved by Wuyun Xiao's noble ideal of being a hero who serves his country and its people, the household guardian immortal helps Erzi champion justice in the streets, robbing the rich to help the poor. With night vision, agility, and razor-sharp claws at his command, the once-timid boy becomes a shadowy cat knight who roams the old lanes and protects the peace of everyday life. He torments thugs and plays tricks on bullies. A bully, furious that Erzi and the great lawyer Mendelssohn ruined his plans to seize the dumpling shop, hires the ronin Okado Nao to murder the lawyer. Enraged, Erzi joins forces with the household guardian immortal and the Cat World's Beggars' Gang to hunt Okado Nao down. The shrine maiden Shino Hekisaiko sneaks into Songpu Wharf, secretly planning to use evil magic to sever the dragon vein. She suspects Okado Nao has encountered an immortal, making him her greatest threat. She battles Erzi and the others with sorcery. The cat immortal's spirit runs out of power and returns to its rightful place, while Shino Hekisaiko dies when her own dark magic turns against her.
Erzi loses his supernatural powers and retires to the countryside with his beloved Yadan'er, where they open a tofu shop. They preserve the warmth of ordinary life, and at last, the dawn shines upon them!
