Lin Shuyue is a twenty-year-old second-year student at the Public Security University who comes from a family of police officers. Her mother died in the line of duty when she was young, and her father, a criminal police officer, sacrificed himself when she was sixteen. Raised by her grandparents, Lin Shuyue is determined to follow in their footsteps and join the police force. During her internship at a newspaper, she encounters a human trafficker snatching a child in broad daylight. She attempts to intervene but is shot by the trafficker, who is carrying a homemade gun. Just as she loses consciousness, a robotic voice announces the activation of the Good and Evil Detection System.
Lin Shuyue awakens in an unfamiliar, dilapidated urban village in Pengcheng on May 20, 2004. She discovers she has transmigrated into the body of another twenty-year-old woman named Lin Shuyue, who is a journalism intern at the Pengcheng Metropolis Daily. The system informs her that her remaining lifespan is critically low, indicated by a red countdown timer. To recharge her life value, she must complete tasks assigned by the system. Shortly after arriving, the system detects a major violent crime at Baoan Street in Suishan Village. A serial killer has murdered two young sisters, leaving their bodies in a gruesome state. The system directs Lin Shuyue to the scene to assist the police in finding the perpetrator, promising one month of life value as a reward.
Lin Shuyue rushes to the crime scene, where she learns from locals that the suspect, Duan Taoyong, is a reclusive neighbor with a history of strange behavior. The police, led by Team Leader Hang Jiabai, are conducting a massive search operation involving armed police and hundreds of villagers. Despite being warned to stay away due to the danger, Lin Shuyue follows the search party into the mountains. Using the system's Good and Evil Radar, she tracks Duan Taoyong, who has escaped the initial search and is hiding in the forest. She witnesses him attempting to murder another villager, Hongzai, who had earlier mocked her for being a woman.
Lin Shuyue intervenes, using a brick provided by the system's newbie gift pack to injure Duan Taoyong and prevent him from killing Hongzai. A confrontation ensues between Lin Shuyue and the armed murderer. She dodges his axe attacks and strikes him with the brick, which possesses supernatural properties that return to her hand when thrown. After a tense battle, she incapacitates Duan Taoyong and blows a whistle to summon the police. Team Leader Hang arrives and arrests the suspect. The system rewards Lin Shuyue with one month of lifespan, three hundred points, a strength-enhancing pill, and one thousand yuan.
Following the arrest, Lin Shuyue learns from a newspaper article dated 2012 that Duan Taoyong had actually escaped in the original timeline and remained on the run for eight years, committing additional murders before his eventual capture. By apprehending him early, Lin Shuyue has saved eight lives. She returns to her new life as a journalism intern, navigating workplace dynamics with colleagues such as the arrogant Li Weisheng and the supportive Li Mingfang. She also reconnects with her new family, including her sister Lin Shuxing and her sister's fiancé, Luo Zhengjun. The story concludes with Lin Shuyue accepting her new reality and her role as a reporter who can serve justice through her profession, while the system continues to guide her actions.
