Mi-sook raised her son Tae-ho alone after being widowed early by her husband. Then there was a man who comforted her lonely heart, and he was none other than Hyeon-dong, her son's best friend! For his son Tae-ho, who still doesn't know anything about this, Mi-sook suggests that they go on a trip with her high school alumni, Se-ryeong and Eun-hye, and tries to carry on her dizzying relationship with Hyeon-dong.