This was a sequel to one of PRC's biggest hits, "The Devil Bat" (1940) that was released six years earlier, but it ignores the plot of the original film. Nina is finally relieved to learn that her father, Dr. Paul Carruthers, is innocent of being a "vampire" and "The Devil Bat." In the original film, Dr. Paul Carruthers, played by Bela Lugosi, was gleefully guilty of creating a huge "devil bat" and arranging for it to kill people.
No cast members from "The Devil Bat" (1940) appear in this sequel.
The calendar says that it's Saturday, May 19. That sets the movie in 1945.