Advertising editor Zheng Yuting (Kim Ji-soo) was stabbed 9 times and died tragically in Room 1207 of Gangnam Hotel. The police caught a criminal suspect, Jin Yongxun (Shin Ha-kyun), through surveillance video. At the time of the incident, he was hurriedly carrying a gasoline bottle and preparing to flee the scene. Police officer Cui Yanqi (Cha Seung-won) interrogated him, and the whole process became a reference video for the TV station's judicial debate. After that, the police began to collect witness testimonies extensively, including gas station employees, Japanese passengers in the elevator, hotel owners and waiters, blind masseurs, colleagues of the deceased, and even wizards who danced the gods... When the police investigated, they found that the deceased was actually the mistress of the father of a dancer (Park Jung-ah). So they began to suspect that she and her boyfriend (Ryu Seung-ryong) deliberately killed the mistress, but the interrogation ended in vain. In the end, Officer Cui thought he had a sure win, and when he revealed the identity of the murderer, he discovered another truth...