Han Seo Jin, Noh Seung Hye, Jin Jin Hee, Lee Myung Joo all live with their families in SKY Castle, a luxury private town where wealthy doctors and professors live. It was built by the first president of Joo Nam university, which is the best university in Korea. All of the women wish for their children to enter prestigious universities and are actively supporting their education.
One day, Myung Joo suddenly commits suicide following her son's acceptances into Seoul National Unversity as a medical student. The community is shocked by that and Myung Joo's family quickly moves out from SKY Castle. However, the community is even more shocked, when Lee Soo Im and her inferior family move in. Soo Im takes it upon herself to help the stress out children and challenging the other women of SKY Castle.