The story of episode 12 is as follows:

Liu Wusi had a good review before the exam, so he finished it quickly. He was the first to hand in the paper, which caused an uproar. Zhou Wenhai thinks that Liu Wusi peeked at the test paper and his grades dropped. Liu Wusi got high marks. Zhou Wenhai reinforced his guess. He accused Liu Wusi of cheating in front of everyone and peeked at the test paper before the exam. Liu Wusi doesn't know how to defend himself. He is not a talkative man. Sun Fujun believes in Liu Wusi's ability. Because of Liu Wusi's efforts, he saw it in his eyes. He defended Liu Wusi, but Zhou Wenhai insisted that there was nothing Liu Wusi could do. Finally, he came up with a way to prove his innocence. He asked Zhou Wenhai to ask him casually in the reference book to see if he could answer. As a result, he could answer all the questions raised by Zhou Wenhai, but Zhou Wenhai was speechless.

Everyone was shocked by Liu Wusi's ability and applauded him. Yu Yanhua also stood up to speak for Liu Wusi. She talked about the day she saw Liu Wusi in the restaurant. Zhou Wenhai realized his mistake and took the initiative to stand up and prove the righteous act of that day for Liu Wusi. The director sat up, noticed Liu Wusi and asked him why he didn't leave his name. Liu Wusi didn't know how to answer. Sun Fujun gave him a perfect answer. Everyone applauds Liu Wusi's justice again. Liu Wusi almost cried. He was very moved and finally got everyone's approval.

Time flies, four years passed quickly. Zhao Xiaojing and Shen Yongnian have been married for four years, and great changes have taken place in the police station. Many former comrades have been transferred, leaving only Liu Wusi, who will not leave.