Set in 1993 Hong Kong, See Her Again follows the protagonist, a police officer played by Chan, who investigates the case of a seemingly mentally disturbed suspect who he believes may be connected to a series of murders. During a chase, Chan's character steps into an elevator, which suddenly plunges, leaving him in a coma. When he wakes up, he finds that he has traveled through time to 2018.

The officer is even more shocked to discover that his wife and young daughter, who were injured in a car bomb explosion that might be related to the murders, are nowhere to be found, and their former apartment now has new residents. The officer manages to speak to a former subordinate, and comes to believe that the only way to return to 1993 and reunite with his family is if he can unravel the still unsolved serial murders that happened 25 years earlier.

"The script is intriguing," says Chan, who adds that he read it almost in one go.

In one of the biggest twists, the police officer, who has no valid identity card for 2018 Hong Kong, decides to use the identity of a deceased undercover officer to return to the police station with the help of his former subordinate, who has become team leader. The officer's greatest drive is to find his daughter, despite the fact that the child, who had been a kindergartner, would now be a 20-something only a few years younger than himself.