[3] The film is based on "They Creep in the Dark" by Karl Brown, which was published in The Saturday Evening Post.

It stars Bela Lugosi as Dr. James Brewster who is aided by his colleague Dr. Randall (Henry Hall).

The film was announced in November 1942, began shooting in December and was released in March by Monogram Pictures Corp.

Reporter Jeff Carter and photographer Billie Mason are on assignment initially suggested by an odd man investigating the recent disappearance of Dr. Brewster.

After Dr. Randall's butler is murdered and the only clue is a fistful of ape-like hair, Carter deduces that the ghostly sounds they heard may well have been from an ape.

Needing more of the fluid as its effects are only temporary, Brewster and his gorilla go on a killing spree as the odd character appears yet again – saving one of the potential victims.

Carter regains consciousness and while he and the police attempt to break into the secret basement entrance, Brewster is attacked by the gorilla.

[4] The Ape Man was based on "They Creep in the Dark" by Karl Brown that was published in The Saturday Evening Post.

[7] The Daily News also commented on the script declaring that "Monogram's writer didn't have to wipe the dust off of Bela Lugosi's Ape Man, he had to rake the mould off.

[7] A critic for the Los Angeles Times gave a positive review stating that "chill chasers will get a tremendous thrill out of the picture, while the more detached will obtain laughs of out of the slyly satricial moments".