This atmospheric black-and-white film, only 59 minutes long, was directed by Harvey Hart and was the pilot for a failed television series called The Black Cloak.

Critic Leonard Maltin wrote that Dark intruder featured: "Intricate plot and exceptional use of the time period blending with suspense" and that this made it "a one-of-a-kind movie."

In the 1971 Night Gallery episode "The Dear Departed", Harvey Lembeck's character suggests, while reading through a newspaper, going to the movies to see the double-feature Dark Intruder and Destiny of a Spy.

The film opens, after the murder of a woman in dark alley by a mysterious caped figure, on a scene between Kingsford and his friend Evelyn Lang (Judi Meredith).

Kingsford is an expert on the supernatural and, along with his dwarf assistant Nikola (Charles Bolender), is called in by police to uncover the scheme of a Sumerian demon to return to earth and take over a human body.

The dealer, (whose shop has a statue of a multi-armed Chinese god who may be Yu Lueh) shows Kingsford a mummified creature with a hideous fanged mouth which the priest claims is a Sumerian demon.