Suying (Shin Eun-kyung) is an obstetrician. When she and her architect husband Ji-seok (Jung Jun-ho) celebrated their tenth wedding anniversary, she accidentally discovered that her husband had a well-hidden affair. Suying was furious. She secretly investigated her husband's company and learned that the person he had an affair with was a young intern, Suji (Shin In-young). She began to approach the girl with the attitude of "sister". Suying took Suji out to play and patiently listened to her secrets. Soon, the little girl opened up her heart and regarded her as her only confidant. She also confessed her worries about falling in love with a married man. Suying dealt with the girl while proposing a separation with Ji-seok. In fact, it was just a means of playing hard to get. The plan seemed perfect. Ji-seok began to feel that Suji was willful and did not want to lose his wife. Just when Ji-seok was about to change his mind, Suji found out that she was pregnant. Suying, who witnessed the man's weakness and hesitation throughout the process, was also shaken. It seemed that the simple Suji made her feel more pity...