PAUL and JENNIFER HEMDALE have just moved into their dream house. But their happy marriage is about to be put to the test as they slowly discover the secret behind the black room in the cellar. Something else is already living in their new home and it is growing stronger every day. It has claimed many victims including the last owners of the house. Repairmen who journey down into the basement soon meet a horrible end. When Paul is taken over by this demonic entity, it is no longer trapped within the walls and is quick to take advantage of all pleasures of the flesh. Jennifer and her younger sister KAREN begin to suspect that something is wrong with Paul. Karen finds out the truth a hard and painful way, leaving Jennifer alone to fight the demonic entity that has possessed her husband and threatens to destroy her very soul. And Paul is not the only one transforming as Jennifer soon discovers that the black room is not only evil but alive as well and may not be able to be stopped!