Lam Yiu Kwok is a secondary school Chinese teacher. Back then, he was known as a talented student in the school, but nowadays, he has a bad taste in his mouth when he sees his university classmates who are soaring to great heights and playing golf in their spare time. His student Hu Cailan falls in love with him and makes a scene all over the school. Lin Yaoguo, like other teachers, tries to stay out of trouble, but he is afraid that avoiding suspicion too much will make Cailan have a negative mindset, not to mention that Cailan is pretty and sentimental, just like his wife, Chen Wenjing, when she was young. The return of Mr. Sheng, who is in the terminal stage of cancer, causes waves in Lin Yaoguo's peaceful life. With the pressure of teaching and the worries of middle age, the temptation of the color blue is doubly appealing to him. In the face of this situation, what choice should a 40-year-old man make? The dilemma of the middle-aged man is thus born.