When Ouyang Zhong (played by Wang Hexi) went to the suburbs to repair street lights on a rainy day, he accidentally discovered an old telephone booth that he had used in his student days. He tried to dial a number and was able to travel through time and space to connect to his girlfriend Situ Xinxin (played by Fiona Sit) who had passed away 20 years ago. In the following phone chats, Ouyang recalled that when he was in love with Xinxin, he often misunderstood that Xinxin was talking on the phone with others because Xinxin's home phone was busy, and ignored himself. Now he realizes that the man who used to chat with Xinxin on the phone every night turned out to be himself 20 years later... Ouyang recalled that he first met his current wife (played by Tang Baoru) at Xinxin's funeral. However, he didn't know that a bigger secret was waiting for him...