Yang Hyung-wook revealed himself as Big Mouse to Lee Jong-seok, who was on the verge of dying.
Gan Soo-cheol (Kim Dong-won), a former prison officer who became the temporary director of Gucheon Prison, set up a suggestion box to root out the bad habits created by Park Yoon-gap (Jung Jae-sung). Also, a search for the bodies of former prisoners in order to find illegal weapons was also launched.
Of course, there was another purpose. It was to find prisoners with the Big Mouse organization tattoo. Gan Soo-cheol carefully examined the bodies at the scene, while Park Chang-ho watched it through the CCTV screen in the director’s office.
A total of three people were found to have the tattoo, but they were all petty criminals. Park Chang-ho said, “Mark these three closely to monitor who they are in contact with. Don’t get excited with just the tail, wait until the whole body is revealed”. Gan Soo-cheol gritted his teeth as he was displeased by Park Chang-ho, who gave an order to the director without hesitation.
Choi Do-ha, who is in a political crisis after his wife’s drug scandal broke out, noticed that he had been subjected to the same method when he worked with Park Chang-ho in the past. Therefore, he began to doubt whether Park Chang-ho joined hands with Big Mouse or Ko Mi-ho (Im Yoon-ah) got a job in the prison medical office because of Seo Jae-yong (Park Hoon).
Gan Soo-cheol was driven by his desire for power. He not only used direct violence against Park Yoon-gap, who returned as a prisoner, but also caught and tortured three people who have the tattoo of Big Mouse organization. Fortunately, Park Chang-ho, who appeared at the right time and saved Big Mouse organization members, said to Park Yoon-gap, “No one guarantees your life. Even Big Mouse won’t protect you”, threatening him to reveal the identity of Big Mouse if he wanted to be protected.
Gan Soo-cheol told Choi Do-ha that Park Chang-ho teamed up with Park Yoon-gap in order to become an official prison director. He then received permission to catch Big Mouse in his own way.
Later, Gan Soo-cheol gathered the prisoners and told them about the Big Mouse organization tattoo, saying “Park Chang-ho is fake Big Mouse. The real Big Mouse is hiding somewhere in this prison”. He emphasized that the prisoners were banned from using amenities, free time is reduced by half, workload doubled, detention money was also prohibited, and emergency measures would only be lifted if Big Mouse got caught. Especially, those who contributed to the process of catching Big Mouse would be rewarded.
The prisoners, who became more sensitive about the incident, performed violence on Park Yoon-gap. In this situation, Choi Do-ha, who was convinced that Ko Mi-ho was investigating Seo Jae-yong’s thesis, made a suspicious call with Gan Soo-cheol.
After then, Gan Soo-cheol told the prison officer to follow him, “Park Chang-ho and Ko Mi-ho, we have to kill both of them today”. Gan Soo-cheol deliberately created a situation where sensitive prisoners were causing a riot and pulled a gun toward the prison guard during the fuss. He gave the order, saying “Find Park Chang-ho and kill him with this. Ko Mi-ho will be killed by a mob of the prisoners and you have to defend yourself”.
Meanwhile, Park Chang-ho met with Big Mouse. Earlier, Noh Park (Yang Hyung-wook) appeared in front of Park Chang-ho, who told Park Yoon-gap “Tell Big Mouse to come to the cathedral at 8 p.m tonight” or else he would overturn all the plans. At the appearance of an unexpected person, Park Chang-ho tried to confirm his identity again, asking “You are Big Mouse?”. Meanwhile, Jerry (Kwak Dong-yeon), who received someone’s call said, “That’s interesting, Chang-ho hyungnim”, and showed a suspicious smile, making the viewers more curious about his identity.