What is H.P. Lovecraft's "The Dunwich Horror" about?
Like most Lovecraft stories, "The Dunwich Horror" involves an unnamed, unseen spectre (the "horror" of the title), as well as some rather confusing connections to "The Old Ones"-Lovecraft's favorite evil ancient beings.
The story focuses on Wilbur Whateley, whose birth and development are shrouded in mystery. Wilbur matures at an incredible rate, reaching adulthood in a decade. During this time, his sorcerer grandfather teaches him certain dark rituals and the study of witchcraft. The purpose of this is so that he may open the way for the return of the mysterious "Old Ones", whose leader is Yog-Sothoth. there is some unseen being in the house (the "horror") somehow connected to Yog-Sothoth. Every year, this invisible entity grows, requiring Wilbur and his grandfather to make frequent modifications to their residence. Cattle begin disappearing from the nearby farms. Eventually, Wilbur's mother also disappears. By the time Wilbur's grandfather dies, the colossal being occupies the whole interior of the farmhouse.
Then, it is up to Wilbur to somehow defeat the evil his family has risked their lives to conceal.