A story about a female killer. Kill Bok Soon is a single mother. She is also a lethal killer, with a 100% success rate on contract killings. She works for M.K. Ent, which is run by Cha Min Kyu. He trained Kill Bok Soon as a killer and they hold mutual respect for each other. At the same time, Kill Bok Soon is aware that Cha Min Kyu is a dangerous person who can take away everything from her. Cha Min Hee is the younger sister of Cha Min Kyu and she works as an executive at M.K. Ent. She doesn't show her feelings to other people. Han Hee Sung is a killer for M.K Ent. He is highly skilled at his job, but he is not recognized by others for his work. Right before Kill Bok Soon is set to renew her contract, she gets involved in a kill or be killed confrontation.