Everybody Has Secrets revolves around Soo-hyun (Lee Byun-heon) and three sisters. While he is falling in love with the youngest sister Mi-young (Kim Hyo-jin), he also tries to seduce her two sisters, the "old virgin" Sun-young (Choi Ji-woo) and the married Jin-young (Chu Sang-mi). The three sisters are captivated by Soo-hyun's sweet talk and begin to put morality aside...