Cheng Xiaoshi and Lu Guang run Time Photo Studio and accept requests from clients to relieve them of regrets. Through a photo provided by the client, Cheng Xiaoshi can travel back in time to the moment it was taken and assumes the identity of its photographer, with him absorbing the photographer's memories and emotions in the process. At the same time, Lu Guang has the ability to keep track of the events in time and helps Cheng Xiaoshi relive the experiences of the photographer. The two work under the conditions that they have only 12 hours with one chance to travel in time and find what their client is searching for, while also leaving the events of the past unchanged.