Yeong-eon (Kim Ok-bin), the top singer at an all girls school, is murdered by a music sheet in the opening scene. The day following her death nobody can see or hear her except her friend Seon-min (Seo Ji-hye). After Yeong-eon convinces Seon-min that it is her voice that can be heard the two attempt to find out what happened to Yeuong-eon. The mystery behind her death is slowly unraveled as Yeong-eon has more and more flash backs to her life before her death. There seems to be another ghost that is haunting the school, one that the two friends suspect, must be Yeong-eon’s murderer. Later, Yeong-eon’s body is found in the elevator, the same elevator that a previous student died in. Yeong-eon is running out of time to discover her killer, if her friend forgets about her then she will lose her voice. On the other hand, a girl can also feel her and didn’t know that she wouldn’t die in the end. Yeong-eon didn’t know that when she died, another her (the bad side) was split from her. She didn’t even know her bad side because she can’t remember anything on her bad side. Yeong-eon didn’t even know that she killed her own teacher and killed her own mother. Her bad side told her everything. And Seon-min didn’t realize that Yeong-eon would take over her body…