This chapter presents the case of a 24-year-old woman who presented with 5-year history of hallucinations during night, occurring three to four times a week. It presents the clinical history, examination, follow-up, treatment, diagnosis, and the results of the procedures performed on the patient. The polysomnography (PSG) study has revealed sleep latency of 11 minutes and REM sleep latency of 99 minutes. Sleep efficiency was 81% with normal distribution of sleep stages. Her apnea-hypopnea index (AHI) was 3 per hour and periodic limb movement (PLM) index was 4 per hour. The patient is awake from stage N2 sleep at 2.05am without any obvious precipitating cause. She describes seeing a woman standing by her bed. The EEG showed an alpha rhythm commencing immediately on waking and persisting for several minutes, and a review of the EEG recorded over the rest of the night showed no potentially epileptogenic activity.