Sarah, a young photographer, is by herself on Christmas eve. She's been alone since her husband died tragically in a car accident. Today is the last day she has to spend at home before going to hospital to induce labour. The calm is interrupted by a knock on the door. Confronted by a mysterious woman, Sarah is immediately suspicious, and refuses to let her in; however, the woman will not leave.

Sarah suddenly feels afraid and calls the police. In the gloom outside, the woman watches her through the picture windows. Yet, when the police show up, the woman is gone. With riots raging in the neighbouring suburb, the distracted policemen comfort Sarah and leave. Sarah locks herself away in her house, unaware that the woman is now inside. As she feels her first contractions, she does all she can to fight back this madwoman hellbent on taking her unborn child.