Taeyeon lives with her uncle after the death of her parents. At a young age, she was trained to become a highly skilled killer. Taking the lives of innocent people who had nothing to do with her, Taeyeon have became emotionless and indifferent. But that changes when she meets her last target whom unexpectedly has something to do with the death of her parents. Will she be able to kill him and take revenge for her parents or will she get into a situation that she herself cannot imagine? Will this heart wall that she built come crashing down as she finds herself softening up to this stranger? What a bittersweet revenge it is...