I'm sure part of the problem with this episode was that John Nettles is gone, but that wasn't the only problem. Unlike the early episodes with "classy" characters, the characters in Echoes of the Dead ere all "dead common." The Bride in the Bath wasn't at all believable and neither was the woman in the trunk or the murder of the elderly couple. Also, John's constant babbling about old murders was silly, although not as silly as his babbling to the dog! The plot was ridiculous. People do not start killing everyone around just because they get dumped and in this day and age, who writes love letters? I'm sure the man's fiancee in South Africa had access to the internet which made John Barnaby's "discovery" of the letters ludicrous. Then there was the idiotic donkey farm, which served no purpose whatsoever with the old woman whose past was hinted at but, like just about everything else in this episode, went absolutely nowhere. And speaking of "going nowhere," let's not forget the "peeping Tom" scenes. Although the peeping Tom apparently notified the police a woman was being attacked, it would have been nice if someone (Ben, perhaps) had asked why he was outside spying on her in the first place. This was one of the most nonsensical episodes in the show's history.
One of the things Neil Dudgeon needs to do if he wants to successfully replace his "cousin" in this series is lose the dog! People watch Midsomer Murders for the mystery, not to see some fleabag in every few scenes!