Conductor Sung Jin (Song Seung-heon) and cellist Soo-yeon (Cho Yeo-jeong) in the orchestra he leads are about to get married, but one day Soo-yeon suddenly disappears, leaving only a video to say goodbye to Sung Jin. Although Sung Jin feels very painful for losing Soo-yeon, he is attracted to the cellist Mi-joo (Park Ji-hyun) who replaced Soo-yeon. On a rainy night, Sung Jin and Mi-joo, who long for each other, do something unforgivable at Soo-yeon's house, and Soo-yeon, who was thought to have disappeared, is locked in a secret room in the house where she cannot escape alone, watching them...