With a style and tone that wreaks of the late '60s, this cheap-looking adaptation of an H.P. Lovecraft story plays like an obvious reference to the battle between the establishment and the counterculture. The film stars Dean Stockwell as Wilbur Whateley, a brooding young man who makes a connection with a pretty librarian named Nancy (a very out-of-place Sandra Dee). Whateley wants to get his hands on the Necronomicon, a diabolical book that he believes will help him to open a doorway to a dimension inhabited by unspeakable creatures known as the "Old Ones." Hypnotized by Whateley's spell, Nancy accompanies the man back to his cursed home where he lives with his nutty grandfather (Sam Jaffe) and an unseen "thing" that is kept in an upstairs room. Meanwhile, the Necronomicon's owner, Dr. Armitage (Ed Begley), does some detective work on Whateley when he begins to fear for Nancy's safety. He quickly realizes that Whateley means to sacrifice Nancy in order to accomplish his diabolical plan. Whateley manages to steal the Necronomicon and begins the ritual to resurrect the Old Ones. As Armitage races to stop him, the thing from the upstairs room breaks out and beats a murderous path towards Whateley as well, leading to a final confrontation that leaves a lot to be desired.
~ Patrick Legare, All Movie Guide