Cheng Fu, a recent graduate specializing in cultural relic restoration, travels to the Mingsha Thousand-Buddha Grottoes to apply for a high-paying night-shift restoration job. There, he unexpectedly awakens Xuan Mo, a spiritual entity residing in the murals who takes the form of a black cat and protects the grotto. Using traditional restoration techniques, Cheng Fu repairs ancient murals and suppresses the evil spirits lurking within them. When the Cultural Relics Anomaly Management Bureau gets involved, Shen Henian, a painting thief disguised as an expert, infiltrates the grotto to destroy the seals and attempts to refine the Sand Nightmare. During his investigation, Cheng Fu discovers that his grandfather, Cheng Shouyi, who disappeared ten years ago, has been hiding within the gaps of the murals to protect the seal. In the final confrontation, grandfather and grandson join forces to restore the Guardian Grotto mural using a method of symbiosis with cultural heritage. Xuan Mo burns his own essence to suppress the Sand Nightmare, while Shen Henian suffers a backlash and is captured. Afterwards, Cheng Fu is appointed chief restoration specialist and learns that the nine grottoes share the same origin and that the Sand Nightmare has not been destroyed. He sets out to find the remaining eight grottoes.