The Monster Walks may be the origin of the classic haunted house B-movie. The template. The seed from which all other classic haunted house B-movies grew.
It's all here. A dark and stormy night. A spooky old mansion. A mysterious death. The reading of the will. Creepy servants.
Oh . . . and an ape living in a cage in the basement who harbours an intense dislike of the dead man's daughter. The dead man's screaming, fainting, often hysterical daughter who has returned home for the reading of her father's will. This would be the "monster" of the film's title. The ape; not the daughter.
The real monster, of course, is not the ape, but someone else entirely. Although, to the film's credit, the real villain isn't obvious from the beginning.
This film is worth watching primarily to marvel at how many old horror movie cliches it contains. Other than that, there isn't much to recommend, most notably some racial stereotyping that apparently passed as comic relief at the time. On a positive note, the film is brief. And will only consume 65 minutes of your Halloween preparation time.