Cha Jung-han (Oh Ji-ho) is a detective for a special investigation team who deals with violent crimes that include drugs and gangs. One day, his sister and brother-in-law pass away in a severe car accident. Even without time to feel grief, he takes in his baby niece, Eun Ae. For this tough guy, raising a baby is harder than arresting criminals. While struggling to raise Eun-ae, Jung-han re-encounters his first love, Han Ye-seul (Lee Soo-kyung) who is a single mother with her 5-year-old son.