Inspector Diana (Jessica Hsuan) has been working in the logistical position of file management. After she meets the original police officer Chan San-yuen (Teng Li-ming) and the male god of the Flying Tigers, Monk Hansen (Moses Chan), she is arranged by her boss Wai Chin-chiu (Hui Shiu-hung) to join the cold case team. Together with a group of police officers with their own "characteristics", they investigate cold cases that are not paid attention to by the outside world under the leadership of Hansen. Hansen is dissatisfied with Anna and they fight each other until it is revealed that Anna is afraid of using a gun because she was held hostage, which makes the two of them fall in love! Anna meets Lau Tat-wah (Lo Tsz-yi), a cram school student who was brutally murdered many years ago, but he has joined the underworld... Driven by love and guilt, can Anna get back her gun and cheer up again to become a new generation of "armed officer"?