Chaney Jr. plays a neurologist, Dr. Mark Steele, who loses memory of the past few days after learning that his wife has been brutally murdered.

Aware of his wife's infidelity and believing he could be the killer, Steele asks his office nurse Stella Madden to help him recover his lost memories.

When Maria returns home one night in the early morning hours after a rendez-vous with her lover, Mark finally tells her that he has had enough and that he wants a divorce.

Duval's disabled wife (Fay Helm) pays Mark a visit, trying to convince him to help her prove that her husband is innocent.

Curious and craving for information Mark visits the incarcerated Duval and finds out that he borrowed $10,000 from Maria in order to pay off some gambling debts.

[clarification needed] She also admits having tried to burn down the medical office, destroying numerous records, to cover the fact that she had been embezzling from him.

[2] 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.

[2] 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.

[1] Dein had previously worked on various mystery films such as The Falcon, Lone Wolf and Boston Blackie series.

"[7] The Inner Sanctum Mysteries feature a "stream of consciousness" voiceover which Dein stated he incorporated into his script at Lon Chaney Jr.'s insistence.

[7] 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.

"[13] The Hollywood Reporter found LeBorg's direction was "filled with imaginative touches and extracts a maximum of suspense from the psychological plot" and that Chaney "gives an arresting portrayal of the doctor.

"[13] From retrospective reviews, the authors of the book Universal Horrors declared the series "feeble melodramas with little to recommend them beyond their camp qualities and the morose spectacle of seeing a badly miscast Chaney struggle his way through acting assignments that were painfully beyond his depth.