This will be one of those posts in which only I have any interest whatsoever. Sorry.
I adore David Suchet's portrayals of Agatha Christie's Belgian detective for British satellite television. Suchet has filmed nearly every Poirot story and hopes to finish them out before retiring. Most of the short stories were filmed in an hour-long episodic format in the early and mid ninties. The longer stories are shot as TV movies.
One of the longer stories, Sad Cypress, first aired in late 2003. If you do not know the story and don't want it spoiled, you should go away now. In Sad Cypress Elenor Carlyle is accused of (and indeed tried for, convicted of, and sentenced to die for) the murder of Mary Gerard, a romantic rival. The trial concluded that she had poisoned a fish paste sandwich with morphine, which she then fed to the unfortunate Miss Gerard. Miss Carlyle did not press her defense very strongly, because she had actually fantasized about killing Miss Gerard with the fish paste and felt, when Miss Gerard did in fact die, that her desire had made it happen.
In Poirot's dénouement, the sleuth proves that the fish paste was not the vector for the poisoning of Mary Gerard with the following exposition, which is one of my favorite scenes in all of the Suchet stores. It really has to be seen to be appreciated, but if you'd like to do that, you'll need to get it from Netflix.
POIROT: Now this person has the phial of morphine, and the chance, it comes! And this is what he finds. Poirot unveils a plate of six small, triangular fish paste sandwiches, each wholly indistinguishable from the others. POIROT: The sandwiches. One of salmon paste, the other two of shrimp and crab. Alors, our murderer approaches the sandwiches, and at once he observes that the color and the texture are identical. So which one is the salmon paste, eh? Poirot lifts the plate of sandwiches and sniffs them delicately. POIROT: Non, there's no way on earth he could distinguish by smell. So, what can this person do? I am afraid that there is only one thing he can do. Poirot produces a tiny silver spoon. POIROT: He tastes. Poirot proceeds to taste the fish paste filling of each sandwich, producing a more pronounced facial expression of disgust with each taste. POIROT: It was bad enough the first time! But then, suddenly I realised how stupid I had been! I, Hercule Poirot, had followed my reasoning, yes, but I had failed to take into account the madness of the English palette. For, gentlemen, what do we find? We find that we are entering into the realms of lunacy. I do not care if our murderer had the palette of a master chef, he could never distinguish between these slurries! No, it is a fact. These sandwiches are all but indistinguishable. So, I come to the conclusion. I, Hercule Poirot, do not care what was said at the trial! This could never, ever be the practical method of murder! DR PETER LORD: So Elenor Carlyle did not poison the sandwich? POIROT: No she did not. DR PETER LORD: Who did? POIROT: Nobody. TED HORLICK: So it was an accident? POIROT: No, no, no, no, she was murdered. But not by these disgusting sandwiches.