This was actually a reworking of a preexisting script. The original plan had been to set the story in New York, where both Kolchak and Vincenzo had wound up after being kicked out of Seattle. Also, the vampire was going to be Skorzeny, last seen in the original movie, mysteriously back from the dead. Then, word arrived that Kolchak had been green-lit for a series, so the story was reworked into its present form.
The house that the real estate agent is showing at the beginning happens to be Ken Franklin's house in Murder by the Book (1971). It was also used in The Most Crucial Game (1972), as well as a number of other Universal productions, including Quincy M.E. (1976), and The Rockford Files (1974).
Suzanne Charny (Catherine Rawlins) does not speak throughout the episode, with the exception of her hissing at her potential victims.
The estate/house where the vampire (Catherine) hides at the end of this episode is also the location of the Cort estate in "The Norliss Tapes" (1973) which is also a Dan Curtis production.
The female vampire in this episode was described as having gone to Las Vegas three years earlier and was turned into a vampire around that time. This could have been around the same time that Kolchak faced off against the vampire, Janos Skorzeny. This could imply that the vampire, Catherine, was an overlooked victim of Skorzeny.