The below are ranked simply on my sense of their overall effectiveness as entertainment. Although like many viewers, I generally prefer the "Tom" days to the "John" days, that's not an absolute. You'll see that a few of the "John" episodes rank well, one of them cracking the top twenty; still, yes, the older stuff crowds the top half of the list.
The mass of pretty-good episodes in the middle are listed without comment for now, but the best and the worst have some notes or explanations as to why I ranked them as I did. Okay, here goes.
Everything is at its best here. We get a plot that's complex without being quite convoluted, a generous body count, interesting characters who interact believably, lots of dark humor, strong production values, and a satisfyingly bittersweet resolution. There's even a sort of Hitchcockian MacGuffin.
One of several episodes leveraging an unusually strong cast of guest stars, most notably Anna Massey as a high ranking intelligence officer and eventual deus ex machina.
Bernard Hepton was larger than life while playing someone trying to be larger than life. It doesn't seem like that should work nearly as well as it did. The murder method is not for the squeamish to watch.
Solid story; another strong supporting cast; Tom hilariously reacting to the discovery of a corpse with "oh, for heaven's sake." Most people remember this one for Orlando Bloom's appearance before he was Legolas, but it's Timothy West who quietly and expertly propels the episode to its strange conclusion.
One of John Nettles' professed favorites because of the wine trebuchet; a plot slow to emerge but which makes perfect sense when it does; the writers making peak exploitation of the brief grudging-buddy relationship between Barnaby and Scott. Don't forget the yogurt, sir.
A departure from the show's usual formula, with some masterful storytelling.
A memorable performance by Olivia Colman, and an entertainingly tawdry and adulterous side plot.
Iconic season one production, heavy on the sexual deviancy angle.
A quality episode in every respect, and Richard Briers was the kind of actor who could turn goat piss to gasoline anyway.
We all know this one, the pilot that introduced us to Caroline Graham's world and set the tone for the series.
Not on a lot of people's lists of favorites, but it's an exceptionally well crafted episode with a great cast and a light touch, and the chemistry between Jones and Barnaby is at its best.
The "Two Barnabys" episode. Some of the finest dialogue in all of MM was written for it.
A rather adult story that clicks. When a character can say "I miss about eight inches of Larry; I'm not referring to the size of his brain," and we find ourselves reacting with empathy rather than prurient eye rolling, they've done something right.
An engrossing plot with some nice twists; some auction-house intrigue; a fun moment when Jones gets transfixed by a glimpse of a nude model. Look for a couple of Pride and Prejudice veterans among the cast. And one I was surprised to remember from Never Say Never Again.
A bell-ringing competition descending into serial murder might be the most Midsomer thing ever. It might seem like a less than convincing scenario, but we buy it mostly by virtue of Adrian Scarborough's over the top performance. This also marks the first of Clare Holman's three fine guest appearances.
The prototypical old-families, old-money episode. There's drama simmering under all that surface boredom.
Memorable guest appearances include one from Hogwarts' Mister Filch and one from a future Superman.
A John Barnaby episode that reeks of Agatha Christie in all the good ways.
A somewhat unassuming but well executed story. You know you can trust me. I'm the pool man.
Here is one of the show's creepier installments, carried off by a strong cast including Robert Glenister, Celia Imrie, and Alan "Voice of the One Ring" Howard.
Interesting dysfunctional family dynamics among the suspects, and we get to see a jealous Joyce too.
Another unlikely premise, but it produces one of MM's best-drawn villains, and some of the funniest moments of the series.
Juliet Aubrey and Clare Holman shine in what happens to be one of the very few episodes with convincing child actors. Fact.
One of my favorite recurring plot devices is when our hero gets taken off a case by his superiors and keeps working on it from the outside anyway. We get some especially good Troy moments in this one.
An audacious plot with an unexpected and satisfying resolution. Por-TOE-vah.
The best of the cult-themed episodes, featuring a top performance by Stuart Wilson as the eponymous Magician.
There's a rather extravagant cast in this one, and everybody delivers.
Another story worthy of Agatha Christie, one that could easily have been a Poirot vehicle.
Easily the best of the musical episodes. My minor complaint here is that Peter Capaldi is so unconvincing as a conductor. Remember that time Robert Redford tried to play a baseball slugger?
An engrossing episode about greed, academic freedom, bicycling, and buckets of paint. There's an inspired guest performance by David Haig, and John Nettles gets to briefly revisit his Bergerac days, playing an action hero in an exotic car.
The pleasure embodied in Honor Blackman's character is infectious.
Contrast against the "Breaking the Chain" episode. This is how you do a murder mystery around a sports theme.
We get some rare insights into Tom's inner life as he exits the stage.
You don't have to understand the game of cricket to appreciate this well constructed story. Oh, and there's some religion-driven erotic interaction going on between a couple of characters, which might or might not be your bag, baby.
In a throwback to some of the show's early writing, the plot is tight and not littered with irrelevant herrings of whatever color, and the villain's character is among the best.
Jones really shines in this story about an undercover assignment. And I'm not just talking about his exposed bottom.
If you're going to steal a literary plot, you might as well steal from Shakespeare. Happily, Ophelia survives.
Sorry Nelson, she is a bit out of your league.
A kind of parallel story to S6E1 "A Talent for Life" except this time it's a hedonistic old man driving the chaos — in a loin-instigated way.
Julia McKenzie plays a role very unlike her now-familiar Miss Marple. And so much depends on the evidence of a rabbit.
A tightly woven plot, and a source of what would become several signature Midsomer tropes. It arguably has the highest body count of any episode, depending on your criteria.
You're just jealous because I've got a coconut and you haven't.
It kinda almost works, but feels like they must have started out by throwing darts at a wall covered with post-it notes. "Competitive dancing, bionics, PTSD. Go!"
Tom Conti is the most interesting guest star of season 23, and the one reason to watch this otherwise unremarkable episode.
A pedestrian plot. An unconvincing motive. An hour and a half during which you could have been doing something useful.
A must-watch for those who crave that elusive combination of extreme unpleasantness, extreme implausibility, and complete lack of humor.
If you're going to give us a slate of characters who are so unlikeable that we stop caring either whodunit or whom they dunit to, at least try to make the story funny or sexy or something.
I just couldn't let myself suspend disbelief while watching this one. The child actors were not able to convincingly pull off the required personas, and in the end the whole production felt — to join two words that don't normally go together — ineffectively exploitative. There's nothing here that would make me want to rewatch it.
Dumbest motive ever. Being analytical and skeptical isn't exactly a classic spur to madness and murder. Nor does making such a character cartoonishly overact at the end help to sell the idea.
Maybe they looked at S7E3 "The Fisher King" and thought it would be a good idea to scare up some more ancient folklore to drive the plot. I can't fault the idea, but the story fails to generate any plausibility, and the villain is an uninteresting goon.
There's only so much you can do with such an inane premise. Mark Williams, the one bright spot in this mess, puts it best in his opening soliloquy: What a load of utter cobblers. Oh, and our perp hysterically waves a gun around at the end to manufacture drama, which is about the laziest trope there is.
It might have been just watchable from a story standpoint, if it didn't suffer from such overwrought acting.
Feed enough variations of "bicycle racing murder mystery" into a suitable AI agent and you'll have a fair shot at making a better script.
Alas, something had to be at the bottom, and Blacktrees takes la grande framboise. The characters seem to be no more than the one-dimensional sum of their exhaustingly overpaced lines. Little thought was given to plausibility (who knew you could rig a ventilation fan to pull oxygen out of a room!). Pointless, nonsensical optical effects are smeared over the murder scenes. Annette Badland is the only cast member who can pronounce nuclear, while the pathologist she portrays, Fleur, doesn't know the difference between suffocation and asphyxiation. There's an early line from Sarah that is so stunningly stupid that we half expect John to reply (a la Hillary Flammond in Top Secret), "It all sounds like some bad movie!" — after which both of them should slowly turn for a guilty gaze into the camera.