One night Yoo Bang enters a dark, mysterious villa with nothing but a flashlight, only to find an executive of the Chunha Medical Group, Ho Hae slouched in a chair, dead and Jin Ho Hae's niece, Yeo Chi hiding behind a curtain. At Ho Hae's funeral, Yoo Bang and Yeo Chi are suddenly taken into custody for his murder. We're taken three months into the past to reveal what led to this murder and exactly who was responsible. During this flashback we meet Choi Hang Woo, a director from Ho Hae's rival pharmaceutical company, who is undercover to steal the formula for their new drug and the Chief Researcher from Chunha Group, Cha Woo Hee. The lives of these individuals will all be intertwined within these three months to reveal exactly just who murdered Ho Hae, and why.