"Partner" centers around two law firms as they struggle to defend the accused and those around them. Kang Eun-ho, a widowed single mother & attorney, tangles with the charismatic and ruthless attorney Lee Tae-jo. In the first two episodes the attorneys work on cases involving a step-brother chraged with murdering of his step-sister and a lawsuit between a wealthy mother-in-law and her divorced daughter-in-law. Each successive episode will cover provocative cases like these, while also bringing to light the charms of the attorneys and their daily lives.

Oh Yeon Doo is an optimistic online lecturer who teaches the Korean language. After going through many hardships, she finally gets a stable home and career which allow her to prepare for marriage. However, a new dilemma of becoming a single mother occurs. That is when she meets her doctor, Gong Tae Kyung. Although he chose to be a misogamist, a man who wishes to avoid marriage and a woman who is willing to birth a baby without a father starts a relationship. Hence, the contract romance begins with the baby as collateral. Would their impudent lie be able to fool their families to the end?