Will a killer-turned-veterinarian and a detective find a common ground? Kim Soo Hyun is a veterinarian who was once a professional killer. Nobody in the public knows anything about him as a killer, including his age, name and race. Deep inside, he constantly looks for love, but struggles to develop and maintain any pure relationships around him. Do Hyun Jin is a brilliant detective working in Seoul, who graduated from police academy as the most excelled. Although she looks cold and stern on the outside, she is in fact a very sympathetic individual. Hyun Jin trusts her instincts and isn't afraid to rely on the things around her to make a decision to the best of her abilities. She has suffered trauma but still keeps pushing forward.