The Dunwich Horror is a short story by H. P. Lovecraft. Written in 1928, it was first published in Weird Tales, April 1929. (pp. 481–508). It takes place in Dunwich, a fictional town in Massachusetts. It is considered one of the core stories of the Cthulhu Mythos.
In the isolated, desolate and decrepit village of Dunwich, Wilbur Whateley is the hideous son of Lavinia Whateley, a deformed and unstable albino mother, and an unknown father (alluded to in passing by mad Old Whateley, as "Yog-Sothoth"), and strange events surround his birth and precocious development. Wilbur matures at an abnormal rate, reaching manhood within a decade, locals shun him and his family, and animals fear and despise him (due to a smell he gives off). All the while, his sorcerer grandfather indoctrinates him into certain dark rituals and the study of witchcraft.
Wilbur wants to acquire an unabridged Latin version of the Necronomicon so that he may open the way for the return of the mysterious "Old Ones", whose forerunner is the Outer God Yog-Sothoth. Thus, Wilbur and his grandfather have sequestered an unseen presence at their farmhouse; this being is connected somehow to Yog-Sothoth. Year by year, this unseen entity grows to monstrous proportions, requiring the two men to make frequent modifications to their residence. People begin to notice a trend of cattle mysteriously disappearing. Wilbur's grandfather dies. His mother disappears soon afterward. The colossal entity eventually occupies the whole interior of the farmhouse.
Wilbur ventures to Miskatonic University in Arkham to procure a copy of the Necronomicon – Miskatonic's library is one of only a handful in the world to stock an original. The Necronomicon has spells that Wilbur can use to summon the Old Ones, but his family's copy is damaged and lacks the page he needs to open the "door". When the librarian, Dr. Henry Armitage, refuses to release the university's copy to him (and has, by sending warnings to other libraries, thwarted Wilbur's efforts to consult their copies), Wilbur breaks into the library at night to steal it. A guard dog, maddened by Wilbur's alien body odor, attacks Wilbur with unusual ferocity, killing him. When Dr. Armitage and two other professors arrive on the scene they see Wilbur Whateley's partly non-human corpse, before it melts completely to leave no evidence.
The story culminates with the actual Dunwich horror: With Wilbur Whateley now dead, no one attends to the mysterious presence growing in the Whateley farmhouse. Early one morning, the Whateley farmhouse explodes as the thing, an invisible monster, rampages across Dunwich, cutting a path through fields, trees, and ravines, leaving huge "prints" the size of tree trunks. The monster eventually makes forays into inhabited areas. The frightened town is terrorized by the invisible creature for several days, with two families and some policemen eradicated by it, until Dr. Armitage, Professor Warren Rice, and Dr. Francis Morgan, all of Miskatonic University, arrive with the knowledge and weapons needed to kill it. The use of a magic powder renders it visible just long enough to send one of the crew into shock . The barn-sized monster screams for help -in English- just before the spell destroys it, leaving a huge burned area. In the end, its nature is revealed: it is Wilbur's twin brother, though it "looked more like the father than Wilbur did."
"The Dunwich Horror" is one of the few tales Lovecraft wrote wherein the heroes successfully defeat the antagonistic entity or monster of the story, although the Horror itself is only the remainder of a far more fiendish plan thwarted by Wilbur's premature death.