In her past life, security inspector Zhou Lan trustingly dismissed a "bomb joke" made by four college students, letting dangerous equipment through and ultimately perishing in a sea of flames along with her younger sister. Reborn on the day of the incident, she decisively sounds the alarm, withstanding pressure from pleas, doubts, and suspension while holding the line for safety. As the investigation deepens, more dangerous equipment surfaces, with crises successively hitting schools, hospitals, and station warehouses. Joining hands with public security and firefighters, Zhou Lan races against time to rescue others, protecting the safety of the public and her sister, and ensuring that profit-seekers and negligent individuals bear the responsibility.