When a woman is found drowned in the bath the police begin an investigation. However, the victim's ghost goes after the police, and one cop is arrested and sent for psychiatric evaluation as the other cops think he is crazy. With him out of the way the ghost goes after others.
When she was alive, the ghost had a boyfriend and a lover and the reason why she's dead is because one of them killed her out of jealousy. We see her have sex with both, but initially, we don't know who among them was her boyfriend or her lover and it's revealed to us as the movie goes on.