In the summer of 1983, 17-year-old Lin Keming (Shi Zhitian) and Wang Lei (Cheng Yuxi) became acquainted with each other in an English speech contest, and their ignorant feelings sprouted. However, a young and frivolous accident, forcefully separated the two, but also extinguished the throbbing of the first love, and even did not have time to say goodbye, the first love, which was about to say goodbye before it began, ended in this Bee Gees's "First of May". More than 20 years later, the daughter of 45-year-old Wang Lei (Jia Jingwen) and the same 17-year-old white (Cheng Yuxi) make their lives crisscross again. Lin Keming (Ren Xianqi), 45, received a letter from the Internet. a letter that seems to be belated, Wang Lei, let him recall once again, that pure youth, that period of 17-year-old arrogance, and that lonely regret. It seems that this special age is destined to have a special meaning. The 17-year-old is also caught in an emotional confusion. In the face of the boy and the best sister, she does not know how to choose.