Villain(s)  Invisible entity

Actor(s):  Sandra Dee, Dean Stockwell, Ed Begley, Lloyd Bochner

Brief Description  The Dunwich Horror (1970) is an American supernatural cosmic horror film directed by Daniel Haller and executive produced by B-movie icon Roger Corman for American International Pictures. It is a loose adaptation of H.P. Lovecraft's famous 1928 short story of the same name. The screenplay was co-written by future Academy Award-winner Curtis Hanson. Unlike the original text, which reads like a dark academic journal, the film infuses 1960s psychedelic imagery, witchcraft, and erotically charged occultism to match the counterculture style of its era.

Plot:
The film begins at Arkham's Miskatonic University, where Dr. Henry Armitage finishes a lecture on the legendary, cursed book of black magic, the Necronomicon. Wilbur Whateley, a strange young man from the decayed, insular village of Dunwich, requests to examine the university's rare copy of the book. Using a strange, hypnotic gaze, Wilbur temporarily bends Dr. Armitage's will to grant him access. While at the library, Wilbur crosses paths with student Nancy Wagner. He intentionally uses his influence to captivate her. When Wilbur later claims to miss his bus back to Dunwich, Nancy offers to drive him home to his family estate.

Upon arriving at the ominous, isolated Whateley mansion, Wilbur secretly drugs Nancy’s tea and disables her car, stranding her for the night. Nancy falls into a hallucinatory, psychedelic stupor filled with vivid, erotic nightmares of pagan rituals and ancient deities. Wilbur and his grandfather view Nancy not as a houseguest, but as the essential, pure vessel required to open a dimensional gateway for cosmic entities known as The Old Ones. Back in Arkham, Nancy’s friend Elizabeth and Dr. Armitage grow deeply alarmed by her sudden disappearance. Their investigation into the Whateley bloodline reveals a horrifying family history: Wilbur's mother has been locked away in an insane asylum since giving birth to twins.

One twin was Wilbur; the other was an unseen, monstrous abomination. Nancy’s psychological defenses crumble as Wilbur manipulates her into staying for the weekend. In need of the ultimate spellbook to complete his plans, Wilbur breaks back into the Miskatonic University library, steals the Necronomicon, and brutally murders a security guard. Concurrently, Dr. Armitage and Elizabeth arrive at the Whateley manor searching for Nancy. While investigating the house, Elizabeth opens a heavily locked upper-room door. She is immediately attacked and completely devoured by an invisible creature—Wilbur's hidden, monstrous twin brother, the Dunwich Horror.

Deprived of its regular feedings by the family, the invisible monster breaks out of the house and begins a destructive rampage across the Dunwich countryside. Wilbur transports a fully entranced Nancy to a jagged, prehistoric stone altar located at a local landmark known as the Devil's Hopyard. He secures her to the stone and begins chanting the raw incantations from the Necronomicon to summon the cosmic entities, intending to sacrifice her to breed a new race of outer gods. As the sky twists into a supernatural storm, Dr. Armitage tracks them to the ritual grounds. Just as the invisible Dunwich Horror arrives at the altar to reclaim its brother,

Armitage counters Wilbur's magic by chanting a powerful banishment curse. The sky erupts into lightning, striking Wilbur and setting both him and his invisible twin brother ablaze. The cosmic portal collapses, sending Wilbur and the monster down to a fiery death. Nancy is successfully rescued by Dr. Armitage, apparently safe from the cosmic nightmare. However, the final camera shot reveals a dark twist: Nancy is pregnant with Wilbur's child, ensuring that the corrupted, otherworldly Whateley bloodline and the threat of the Old Ones will endure into the next generation.