A stray dog at a crossroads suffered a car accident and was on the verge of death, but was rescued by ordinary office worker Lin Xiaonuan, who named it "Heibao", starting its second life. Recovered, Heibao silently protected its new home and neighborhood with professional skills, smartly cracking a serial theft case, delivering an umbrella in the pouring rain, and jumping into the water to rescue a drowning child, becoming a "guardian deity" praised by the neighbors. Fights and fatigue caused its old injuries to flare up repeatedly, so Lin Xiaonuan posted a notice to find its owner, leading search and rescue instructor Chen to track it down, and Heibao's identity as a retired military working dog was officially revealed. Faced with the choice between returning to the team and staying home, Heibao resolutely chose to stay by its savior's side, and instructor Chen respected its wishes, promising to visit often.