Because of an accident, Li Wennuo and Zhao Xinyi were separated. At the same time, the four friends all had different tragic experiences. When we met again, Zhao Xinyi began to gradually forget what they had experienced together... Li Wennuo: "Zhao Xinyi, let me help you recall our youth." Our youth is the same but special and unforgettable. In such simple years, I met you, Zhao Xinyi, who is not simple. So you became my passerby. In the deep water of life, we met, got to know each other, and became each other's light. However, due to the pollution of PM2.5, The light was covered up, and the mist blurred the already somewhat short-sighted sight. In such a deep pool, two lost sails are drifting away... Zhao Xinyi, I don't know that passerby A will become what he once was.