OK, so maybe "The Private Eyes" is sort of a rehash of "Murder by Death", but it's still a laugh riot. It's essentially what would happen if Laurel & Hardy or Gilligan & the Skipper were detectives investigating a murder in an English mansion. In this case, Don Knotts is the irascible straight man and Tim Conway is his dimwitted assistant, looking into the killing of some aristocrats in a possibly haunted estate. The entire movie is basically an excuse for a series of gags, some clever and some cheap. It certainly made me laugh. As for the obvious plot holes...well, it's just a movie.
Yes, there's nothing special about the movie, but I still liked it. Also starring Trisha Noble, Bernard Fox (Dr. Bombay on "Bewitched"), Grace Zabriskie, Irwin Keyes and Suzy Mandel.