Death was the first film in the "Inner Sanctum Mystery" series. In June 1943, Universal purchased the screen rights to the series from Simon and Schuster, Inc. who were publishers of the popular mystery novels and radio shows. Simon and Schuster were using the title Inner Sanctum for their series of mystery novels they had published starting in the 1930s. The radio adaptations had initially started in January 1941 on the NBC Blue Network and was broadcast weekly. Ben Pivar of Universal sought out a suitable entry for the first film in the series, and purchased an original screenplay by freelance writer Edward Dein titled Calling Dr. Death. Dein had previously worked on various mystery films such as The Falcon, Lone Wolf and Boston Blackie series. Dein later reflected on his work at Universal, stating that he worked there "as a reader for a few weeks, which was another horror story. We called this the Snake Pit. In those days, we were not considered to be prolific writers; we were hacks." The Inner Sanctum Mysteries feature a "stream of consciousness" voiceover which Dein stated he incorporated into his script at Lon Chaney, Jr.'s insistence. Dein stated that Chaney felt the dialogue was too technical and he couldn't say the words. LeBorg stated it was both Chaney and Pivar who suggested it, stating "Pivar was very, very crude, not very intelligent, and he couldn't read very well." Lon Chaney, Jr. was hopeful for the series, craving diversity in his roles after Universal had placed him in various monster roles in their horror films. Pivar planned to produce two Inner Sanctum mystery films a year with each film featuring Chaney and Gale Sondergaard in the lead roles. Director Reginald LeBorg was chosen by Pivar to direct the film, with LeBorg recalling that "Pivar had confidence in me because I was a fighter who tried to get better and better material." Just before filming was set to begin, Sondergaard was dropped from the cast and her role was rewritten and given to Patricia Morison. LeBorg speculated that Sondergaard was dropped from the film as "she was a leftist and she and her husband [Herbert J. Biberman] were shooting their mouths off quite often." Calling Dr. Death went into production on October 25, 1943 and was finished filming in 20 days. Patrica Morison recalled working on the film with Chaney, stating she "didn't get