In just a few short days, 3 'Killing Smile' cases is shocked the whole city. During the investigation, a young but clumsy detective of Police Department named Wang Bu-er issues a shocking statement: 'This is a case of mass murder.' He and the expert inspector Huang Feihong start a terrified and dramatic investigation. Huang Feihong is visually indecent and quite mundane but actually a super grandmaster, he always helps Wang Bu-er to overcome dangers.