When nothing seemed to be able to stop Prosecutor Ma Yi Deum from building a spotless career, an unexpected accident causes her personnel appointment to be canceled. However, this tough cookie of a prosecutor cannot be brought down easily. She meets a newly appointed prosecutor, Yeo Jin Wook, who chose the field of law over practicing medicine. Yi Deum and Jin Wook hate each other's guts, and yet, the two must form a team and investigate criminal cases. As the story develops, the two realize that the fact they have been brought together was not due to ordinary fate. They team up and solve criminal cases together, and at the same time, they try to reveal the truth behind the heinous act that took place years ago. During the process, they come to understand and embrace each other.