A Murder is Announced starts with one of Christie's most audacious set ups, proceeds clearly and logically through a convoluted plot, involving three murders and three different people who are not who they seem to be, and eventually arrives at a satisfyingly elaborate denouement.
In this three-part adaptation of the book Miss Marple tends to flit around on the edge of events and it is not until the end of the first episode that she is actually involved in the investigation. Nonetheless, she still manages to provide the crucial insights that unlock the mystery.
This is a fairly expansive production, so for once a Christie story can be told without too much compression, over-simplification or compromise. However, this means that any flaws in the story must be attributed to Christie, not to the screenwriter. And there is a flaw: a massive flaw.
Charlotte Blacklock realises that Rudi Schertz can scupper her plans to inherit the Goedler fortune, so she decides he has to be eliminated. But why eliminate him in such a showy, elaborate and risky way?
Firstly, as far as anybody else is concerned, there is no possible connection between a Swiss hotel worker and a respectable English woman who just happens to have dined at the hotel a couple of times. If she just kills him on his way home from work there is no reason why she should even be questioned, let alone be regarded as a suspect, so she wouldn't even have needed an alibi.
Secondly, why locate the murder in her own home, with herself as the apparent intended victim? This immediately draws her right into the centre of the investigation and raises the possibility of her imposture being exposed, even if she is never actually suspected of the murder.
Finally, why plan the murder in such a risky way? When the lights go out she has to open a door, slip through, fire three shots in pitch darkness (one of which has to be fatal) and slip back into the room again, without being detected. Given the darkness and confusion, this might be feasible, but only if everything goes exactly to plan – including things over which she has no control. For example, what would she have done if someone had just happened to be standing in front of the door when the lights went out or when she tried to slip back into the room? What if Rudi Schertz hadn't died instantly? What if someone simply noticed her absence (as actually happens)?
These sorts of objections could be raised against many of Christie's most famous stories. The real reason it is often difficult for us to solve her mysteries is that the murders are sometimes so irrational that there is no way the explanation can be logically deduced. Moreover, it is characteristic of Christie stories that the significant clues only make sense retrospectively. Once you know what really happened, the clues all fit, but the clues themselves are not really sufficient to lead anyone (not even Miss Marple or Hercule Poirot) to the explanation of the mystery.
Of course, if you want to enjoy an Agatha Christie mystery you just have to accept that the reasoning is likely to be somewhat tenuous and the solutions are going to be a bit far-fetched. These are just the conventions of the classic 'whodunit'. In this case, I suspect Christie just fell in love with the initial premise and relished the challenge of devising a sequence of events that could have lead up to it. The fact that the premise itself makes no sense is not really relevant. The test of a good Christie story is not plausibility, but ingenuity.
Nonetheless, I do get a little irritated by those IMDb reviewers who object to any changes that screenwriters make to her sometimes preposterous plots. Christie is nearly always good fun and there is no doubt that she came up with some great puzzles, but she wasn't always writing at her peak. Because this series is relatively faithful to her books it soon becomes apparent that some of her stories are significantly cleverer than others and some are actually quite threadbare.
In the more recent Geraldine McEwen and Julia McKenzie series, the screenwriters were allowed to make very free adaptations of her books. This often resulted in radical changes and significant improvements - especially to some of her weaker stories. I particularly like the changes made to Nemesis, At Bertram's Hotel and A Sleeping Murder, where many of the characters are completely new inventions, the mysteries are more convoluted and intriguing and the overall result is more dramatically satisfying.
However, it is quite clear that many people find it inconceivable that you could improve on the 'Queen of Crime' and consider it blasphemous for anyone to even suggest it.
For me, this kind of blanket rejection is not criticism, it is idolatry.
