Ellen receives an exotic mask and begins to have waking nightmares and hallucinations, attacked by a being she refers to as the Nightmare Man. Her husband and doctors believe she is a paranoid schizophrenic and that she needs to be committed. On the way to a mental facility the car breaks down and after her husband rushes off to get gas, the Nightmare Man appears. Ellen flees the car and stumbles upon a country house where two young couples are vacationing for the weekend. But is this man/demon real or is it all in Ellen's mind?
