Class 2B of Harvard High School is the most mischievous class in the school. All previous class teachers could not last more than three months. The principal Dong Renqing decided to take a bold gamble and invited Wang Haonan, a retired police officer, to help. Wang Haonan, who looked like a nerd, made the students playfully bet on how long the new teacher could last. In addition, the students discovered that Wang Haonan had an unusual relationship with Wu Jiali, the teacher of Class 2A. It turned out that Wang Haonan was Wu Jiali's runaway groom, and the former fiancée's love-hate relationship as a teacher began.