In 1993, a serial murder case occurred in Hong Kong. While chasing the suspect, Senior Inspector Yang Guangyao of the Crime Unit accidentally traveled through time and space in an elevator to 2018.

However, during this period, there was no news about Guangyao's wife and daughter, and the previous cases were still unsolved. Thanks to the help of his former boss, Guangyao returned to the police station as an undercover agent and resumed his duties. He met a partner who had a completely different style of handling cases from him.His origins also aroused suspicion.

At this time, a new murder case appeared, and there seemed to be a bigger conspiracy behind the murder case. Many clues reminded Guangyao of the murder case that year. In this adventure, he finally recognized that his partner who was just around the corner turned out to beHis daughter also learned that his wife had been killed after he traveled through time. He vowed to catch the murderer and go back to the past to change everything.