Endore was born Samuel Goldstein in New York to Isidor and Malka Halpern Goldstein. His father was a coal miner, inventor, and investor from Pittsburgh who often had difficulty making ends meet. His mother committed suicide when he was four, possibly due to their unstable and often insufficient livelihood.

Isidor changed their name in an attempt to move beyond the events of the past, and he placed the children in a Methodist orphanage. During this time, Isidor sold an invention and dreamt that his dead wife willed the children to have a European education, so he sent them to Vienna with the newfound windfall.

The children lived in Vienna for five years under the care of a Catholic governess, but when Isidor disappeared and their funds ran short, they returned to Pittsburgh and lived together.

He scraped together money to attend Columbia University, and acquired more by renting out his bed to a wealthier student while he slept on the floor.

He received a B.A. in 1923 and an M.A. in 1925, both in European languages.He later taught fiction writing at the Los Angeles People’s Education Center.

After graduating, Guy married Henrietta Portugal and in the 1930s they moved to Hollywood. Despite his eventual blacklisting, Endore had a fairly successful career in Hollywood, working on scripts or story ideas for big name pictures of the time. He made his name in the supernatural arena, with such movies as Mark of the Vampire and The Curse of the Werewolf (based on his novel The Werewolf of Paris). Although many of his films were at the time derided by critics, they have acquired a cult following in recent years.

Throughout his career Endore showed himself to be fascinated with hypnotism and the inability of characters to control their own actions, centering his stories on supernatural maladies such as lycanthropy and hypnosis. Mad Love, Peter Lorre’s American debut, involves a man who, after an accident, is fitted with the hands of a murderer which try to continue in their gruesome career. His novel Methinks The Lady..., which was made into a movie with Gene Tierney, centered around a woman affected by a quack hypnotist. Even his Fred Astaire and Ginger Rogers comedy, Carefree, still includes Rogers being put under hypnosis.

Endore began his movie writing career in 1935, when he wrote the story for Rumba, an insipid star vehicle for George Raft and Carole Lombard, which was given a scathing review in the New York Times.

From there he began working on horror films. He worked on the screenplay for Mark of the Vampire with Bela Lugosi. He also wrote the 19-page treatment that eventually became The Raven, for which he was never credited. A number of other horror films followed, interspersed with more mainstream films including the Oscar-nominated (G.I. Joe), a John Wayne movie (Lady from Louisiana), and a Ginger Rogers/Fred Astaire picture (Carefree).

His Hollywood career ended in 1969 with a made for TV movie entitled Fear No Evil, for which he wrote the story. It was the first US Television “Movie of the Week” and a success in the ratings, spawning a sequel in later years.

While he attended Columbia, he was heavily influenced towards the political left by Whittaker Chambers, who was a fellow student at the time. Endore was motivated by the Great Depression world he lived in to promote leftist philosophies.

While living in Hollywood Endore was interviewed several times and wrote articles for multiple leftist publications, including Black and White, The Clipper, and New Masses.

Endore was a member of the Communist Party in Hollywood and was investigated by the House Un-American Activities Committee during its search for Communist infiltration of the film industry. He was, however, never called before a “witch-hunting committee” and did not spend any time in jail.

Because of his Communist associations, some studios blacklisted him and he had to sell his screenplays under the pseudonym Harry Relis. (Relis was actually the husband of Endore's wife's eldest sister.) However, he remained defiant, claiming that he was a failure as a human being if he was not subversive to everything HUAC stood for.

After the Khrushchev Report he abandoned the fight against the blacklist, only a few yeas before the reinstatement of many leftist sympathizers in the film industry. This has cast him into obscurity amongst the more prominent pro-Communist writers.Endore also did not create prominent works of leftist fiction, instead choosing to compose what he believed would sell.

He became a devoted proponent to the Synanon Foundation, a controversial southern California commune dedicated to reforming and rehabilitating drug addicts and alcoholics. (Later, as the Church of Synanon, it started its own utopian social movement.) He composed pamphlets and a published history of the commune, Synanon.

He also became a pamphleteer for many anti-racist causes, writing The Crime at Scottsboro about the Scottsboro boys and their subsequent trial, and two works on “Sleepy Lagoon”, known also as the “Chicano Scottsboro”.

Endore also studied and was greatly inspired by Marx, as well as mysticism, yoga, vegetarianism, theosophy, and anti-vivisectionism.

Although more famous for his work in Horror, Endore was a committed activist, attempting to protect with words those who were mistreated by the American culture and legal system. He supported non-governmental drug rehab programs, tried to use literature to illuminate what he considered to be historical oversights, wrote pamphlets in defense of the Scottsboro boys and involved himself deeply in the defense of those arrested in the Sleepy Lagoon trial.

Sleepy Lagoon Murder

During the year 1940 Guy Endore became heavily involved with the case of 17 Mexican teenagers incarcerated for a murder. Although there was scant evidence, a complete lack of eye witnesses, and no murder weapon to be found, they were put away in a wave of hysteria spread through the newspapers of LA. Endore became involved when he looked into the case and was startled by the lack of evidence. He proceeded to write a pamphlet entitled the Sleepy Lagoon Mystery which went over in detail the mistakes and oversights involved in the case. Giving a speech on the Al Jarvis radio show, Endore referred to Sleepy Lagoon as “the name of a disgrace which should be on the conscience of every decent American — and especially every decent person who lives in Los Angeles — because we allowed it to happen here.” To bring his readers over to his way of thinking Endore used scare tactics, threatening his readers that, should they allow this to happen, they could, in essence, be next. For the next year he corresponded often with the defense, gave interviews, and spoke on radio shows in an attempt to help the teens. At the end his attempts were a success and, with the information exposed in his pamphlet and a change in common opinion, the verdict was reversed.