"The Dunwich Horror" is a short story by H. P. Lovecraft. Written in 1928, it was first published in the April 1929 issue of Weird Tales (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.
Wilbur Whateley is the son of a deformed albino mother and an unknown father (alluded to in passing by the 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. 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...