The murder of Im Yoona was driving Police Chief Park Jungsu and his subordinates crazy. It's been two weeks since they found the body, but nothing has come out after that. They have been trying to dig information from the first suspect, who was seen with the victim the night before she was murdered, but he kept talking back.

"It's not me," stated Lee Taemin. He was in the brink of sanity, trying to clear his name from the murder case. It must've felt like nightmare to be suspected as a murderer; and worse for him, the murderer of his own girlfriend. Taemin felt miserable, until he found another suspect. An unlikely suspect, that he himself was not sure of giving the name of.

Choi Jinri – Sulli, his childhood friend. This girl was known for her cheerful behavior, or at least, that was how Taemin has known her. But, what if the old Sulli has changed? What if she's changed because of him?

It's up to Officer Kim Heechul to find out the truth.

Love is a wonderful thing. It brings joy, content, wonderful things, and is the beginning of life alone. But love, it can also be the most destructive monster. For it also brings pain, tears, unwanted feelings, and worst, death.