At the age of 8, Park Joo-Hyeong was adopted by an Italian family. He is now an adult and goes by the name of Vincenzo Casano (Song Joong-Ki). He is a lawyer and adviser working for the Mafia. Endowed with unparalleled negotiating skills and charisma, Vincenzo Cassano lives for revenge. Due to a war between mafia gangs, he flees to South Korea. Upon his arrival in Korea, he uncovers a sinister, deep-rooted cartel and finds himself tackling the problem when he becomes involved with Hong Cha Young. Vincenzo falls in love with her. He also achieves social justice in his own way. Hong Cha Young (Jeon Yeo Bin) is the top lawyer at Woosang, Korea’s leading law firm. She is the sort of lawyer who will do anything to win a case. She is more concerned with how advantageous or disadvantageous a situation is for someone than with whether they are good or bad. She begins to change after meeting Vincenzo Casano. Jang Jun Woo (Taecyeon) is an attractive and intelligent trainee at a law firm who has lived abroad. He has a carefree smile, is polite, hard-working and innocent, but sometimes makes comical mistakes at work. He has absolute trust in Hong Cha Young, his senior colleague, and the arrival of Vincenzo Casano sparks his competitive spirit.