The series was cancelled because Darren McGavin asked to be released from his contract. He became disappointed with the series' scripts and was exhausted from his uncredited producing duties. Three scripts were left unproduced. Two of them were adapted into a "Kolchak" series of comic books in 2003.
Producer Dan Curtis and screenwriter Richard Matheson were both approached by Universal to work on the series. Although they had worked on the original made-for-TV movies, they both turned down the offer.
Ruth McDevitt's character is referred to variously throughout the series on-screen by various characters and in the cast lists as Emily Fenwick, Emily Cowels, and Edith Cowels. They eventually settled on the name "Emily Cowles." Her character's occupation also alternates between advice columnist, riddle feature writer, and crossword puzzle editor.
Actor Richard Kiel, before he became best known as the killer "Jaws" in the James Bond movies, was cast in two episodes as the monster. He first appeared as the "Diablero" in "Bad Medicine" and later as the swamp monster in "The Spanish Moss Murders."
Darren McGavin is often incorrectly considered to be, and listed in many official references guides, as the show's Executive Producer. In fact, he never held the position, although he unofficially assumed many of the duties. This put him at odds with Paul Playdon and then Cy Chermak, the official producers appointed by Universal.
Actress Ruth McDevitt not only plays columnist Miss Emily in the latter episodes (the character is on vacation early on), but she appears as an elderly Peeping Tom in the first episode... who writes a letter to the Miss Emily column.