Se-ran (Choi Ji-hee), the mistress of Hyeon-ma (Nam Koong-won), lives in a massive traditional-style house called "Blue Mansion"in the suburbs of Seoul with her sister Mi-ran (Yoon So-ra) and their maid (Yeo Wun-gye). One day, Hyeon-ma comes to the house with his newly-employed male secretary Dan-ju (Hah Myung-joong).