Jung-wan, Sun-mi, and Ji-hyun were high school classmates. Twenty years on from high school at the age of 39, the three friends are leading completely different lives although they are as close as sisters. Jung-wan who was the first to marry is now divorced, while Sun-mi who choose career over marriage is now a successful interior designer but is desperately lonely. Ji-hyun, who married a successful businessman, maintains all outward appearances as a good wife and mother but feels like she is dying inside. What happens when love comes knocking on their doors once again? Jung-wan tried to throw herself into work to forget her ex but meets a new man. Sun-mi is desperate to get married before she turns 40. Ji-hyun, tired of a dull marriage, is reacquainted with her first love which tempts her heart to beat. Love has come once again to the three 39 year old women. Can they fall in love again?