The Deal (2015)
Tae-soo has been a lazy policeman, but accidentally he runs into Kang-cheon, whose car is covered with blood. Tae-soo suspects the worker to be the serial killer that kills young women for months. But as they can't find hard evidence, Kang-cheon is allowed to go. Short time later Tae-soo's sister is found raped and murdered and the detective knows who's the one to blame. But as he can't arrest Kang-cheon, he is searching for vengeance aside any legal term. On his own private investigations, he meets Seung-hyeon who lost his wife to the killer. Together they wanna see Kang-cheon suffering and dying for his murders.