The dialog makes repeated references to Emily, Warren and Helga being in Denmark. At the time this film was produced, the early 1960s, Denmark was the only place where competent transsexual operations were being routinely performed.
Helga is decapitated on a staircase with a surgical knife. But shortly afterward, when Miriam goes up those same stairs, there is absolutely no sign of blood on the carpeted steps or adjoining wallpaper despite the very messy nature of such a murder.
Prologue Host: We've been to Haunted Hills, and through Tinglers, and even Ghosts... but now we're going to meet a group of people who just happen to be... Homicidal.