Since childhood, Jessica has been plagued by recurring nightmares in which she is chased by a mysterious creature called "Horsehead.' In the hope of finding some peace, Jessica has started studying the psychophysiology of dreams. After her maternal grandmother dies, Jessica is obliged to return to the family home. When she arrives, she discovers that her defunct grandmother be laid out in the room next door to hers during the wake. Her first night home, Jessica is once again assailed by the nightmare and suddenly falls ill. Confined to bed with a high fever, she decides to use her lethargic state to experiment with lucid dreaming, and to thereby try to take control of her nightmares - a dangerous practice from which some people never quite recover. Jessica then starts evoloving in her own dream world. She undertakes an investigation in order to at last discover the evil that has been eating away at her and her family for generations. She must also confront, one last time, the evil Horsehead.