The film focuses on a scientist (portrayed by Clarke) who is exposed to a radioactive isotope and soon finds out that it comes with horrifying consequences.

The crew was made up of University of Southern California film students, while the cast consisted of unknowns in addition to Clarke's family and friends.

Distributed by Clarke's own Pacific International Pictures, The Hideous Sun Demon premiered on August 29, 1958 as part of a double bill with Roger Corman's Attack of the Crab Monsters.

When research scientist Dr. Gilbert "Gil" McKenna (Clarke) falls unconscious after accidentally being exposed to radiation during an experiment with a new radioactive isotope, he is rushed to a nearby hospital.

Attending physician Dr. Stern (Robert Garry) is surprised to find that Gil shows no signs of burns typical for five-minute exposure to radiation and informs Gil's co-workers, lab assistant Ann Russell (Patricia Manning) and scientist Dr. Frederick Buckell (Patrick Whyte), that he will keep the patient under observation for several days.

Buckell soon receives word that noted radiation-poisoning specialist Dr. Jacob Hoffman (Fred La Porta) has agreed to help Gil and plans on arriving in the area within a few days.

When radiation poisoning studies offer no leads on solving Gil's own particular symptoms, the distraught scientist contemplates suicide, but soon changes his mind.

When bar patron George insinuates that he has purchased Trudy's company for the evening, Gil defends her, causing a fight between the two men.

Hiding inside an oil field shack while police comb the area and set up roadblocks, Gil is discovered by young Suzy who offers to fetch him cookies.

Mortally wounded, the mutated Gil falls several stories to his death while Buckell, Hoffman and a sobbing Ann watch in dismay.

Development for The Hideous Sun Demon began after the 1957 release of The Astounding She-Monster, a science fiction film starring Clarke.

[2] According to Clarke, the film's plot was inspired by Robert Louis Stevenson's The Strange Case of Dr Jekyll and Mr Hyde, which dealt with multiple personalities.

[6] The initial draft would feature an alternate plot, centering on an explorer and a female lawyer searching for uranium in the country of Guatemala.

[6] The rest of the cast consisted mostly of aspiring actors and actresses from around USC, with additional characters played by Clarke's friends and family.

[1][11][14] Actress Nan Peterson, in her acting debut, was cast in the role of Trudy Osborne because of her voluptuous figure, according to Clarke.

King, however, did write and perform the song "Strange Pursuit", featured in the bar scene in the film, providing the vocals for Peterson's character.

[19][13][14] A scene in the film where a transformed McKenna graphically crushes a rat with his bare hands was not in the script, and was improvised while on location.

Conditions inside the suit were very hot; combined with the humid weather, this caused Clarke, who performed his own stunts in the film, to sweat profusely.

Clarke's brother – a sales manager at an Amarillo, Texas, television station – put him into contact with the owner of several local drive-in theaters.

[30][31] The Hideous Sun Demon was released on VHS as a part of Elvira's Movie Macabre by Rhino Home Video on September 8, 1993.

[30] Bob Stephens of the San Francisco Chronicle, in a 2000 review, criticized the film's narrative slightness and Peter Similuk's casting, but also wrote that he "must confess that I enjoy Demon.

[36] TV Guide gave the film a negative review, awarding it 1.5 out of 4 stars and calling it "laughable", but also commented that the monster costume was good.

[38] Author Jeff Rovin called it "a clever twist on the Wolfman theme" and an "effective and gritty film [that] boasts an excellent monster costume".

The plot centered on a man (presumably McKenna) transforming into the Sun Demon and terrorizing several people before falling to his death off a cliff.

The original film's soundtrack was later added to the remake during post-production, with Glut's friend Bart Andrews supplying the Sun Demon's voice.

[43] Writing for Cinefantastique, David J. Hogan described plans for the original footage to be redubbed using a new screenplay written by Mark and Allan Estrin, with Clarke's character Gil renamed Ishmael Pivnik.

New footage for this version was shot with Clarke's son Cam along with Googy Gress, Mark Holton and Susan Tyrell.

[48][35] Image Entertainment released this film on DVD twice in 2003, first by itself on July 15, and later as a double feature with The Hideous Sun Demon on December 30.

[53][54] The book features an introduction by the film's producer Robin C. Kirkman and a lengthy production history by Tom Weaver.

According to Golden, he previously wrote a short story titled, "I Was a Teenage Hideous Sun Demon", which he described as a "dark satire" of the film.