Hae Joo did not grow up with a silver spoon in her mouth. She has had to study and work hard to achieve success as an oceanographer in the male-dominated shipbuilding industry. Kang San, on the other hand, is the son and heir to the major corporation that she works for. Hae Joo’s first love, Chang Hee, also makes something of himself through sheer determination but is still hung up on Hae Joo. Will a family secret change the course of Hae Joo’s life and everything she has worked so hard for?

The old-timer Bae Tae Sik butt heads with Han Jin Woo acting as the genius medical examiner. The two always differ in opinion, but whenever a case needs to be solved they respect each other’s strengths and act as an unbeatable duo.

Kim Sun Kyung is a retired police officer and father of three sons, Gun Kang, Hyun Chal and Yi Sang.

His eldest son Gun Kang made many wrong decisions in life, ending up being divorced and going bankrupt. Gun Kang gets remarried to Chung Nan. His second son Hyun Chal is the envy of the town and pride of his father. He runs a number of businesses which are quite successful. His wife Woo Mi often sacrificed her happiness for the benefit of the Kim family. As for the last son Yi Sang, he follows in his father's footsteps by becoming a police officer. Oftentimes the father and the son clash each other. As Yi Sang married Eo Young, the daughter of his father's deadly foe, an ex-convict Sun Kyung traced and eventually arrested a long time ago.

"Three brothers" revolves around their relations full of conflicts and love.