Nightmare Man (2006) on Netflix

Plot summary

After a demonic African mask arrives in the mail, Ellen is attacked by a being she calls the Nightmare Man. Her husband William and her doctors dismiss the attacks as paranoid schizophrenia, and they set out to take her to a psychiatric ward. Their car runs out of gas on the road, and William leaves on foot for a gas station. Ellen waits alone in the car, is attacked again, and escapes into the woods. She reaches a country house where two couples are spending a weekend away and tells them a killer is outside. Wary, the couples telephone William, who warns them that she may be dangerous and promises to come.