Dreams in the Witch House

"The Dreams in the Witch House" is a short story by H. P. Lovecraft, part of the Cthulhu Mythos genre of horror fiction. Walter Gilman, a student of mathematics and folklore at Miskatonic University, takes a room in the Witch House, a house in Arkham thought to be accursed. The first part of the story is an account of the history of the house, which has once harboured Keziah Mason, an accused witch who disappeared mysteriously from a Salem jail in 1692. Gilman discovers that for the better part of two centuries many if not most of its occupants have died prematurely. The dimensions of Gilman's room in the house are unusual, and seem to conform to a kind of unearthly geometry that Gilman theorizes can enable travel from one plane or dimension to another. In his dreams Gilman is taken to a city of Lovecraft's "Elder Things", and even brings back tangible evidence that he's actually been there. Several times his dreaming self encounters a bizarre "congeries of iridescent, prolately spheroidal bubbles", as well as a trapezoidal figure, both of which seem sapient. It is hinted that these may be the extra-dimensional forms of Keziah and her familiar.