This is an unusual episode for a few reasons;it has an unusual criminal, Poirot apparently spends much less time detecting than he usually does, but more than anything, what strikes me about this episode is its mournful tone. From the first scene, where we see Russian Countess Rossakov entering her hotel room and looking out the window in an unhappy way, to the last scene, where Poirot sees the Countess off as she boards a train, this episode is much less lighthearted than other ones. Now, I wouldn't necessarily have an issue with that in itself. There are other, similarly mournful episodes that I quite like (The Cornish Mystery and The Plymouth Express come to mind). But in this case, Christie, in her original story creates Countess Rossakov as an extraordinary character: flamboyant, passionate, melodramatic, in fact, all the things that Poirot is not.(I visualize her as a kind of "Dynasty" era Joan Collins, all shoulder pads and feather boas.) And yet even in the story he is bowled over by her in an "opposites attract" kind of way, that I desperately wanted to see play out on screen. In this episode, there is a moment where the Countess acknowledges that she and Poirot are opposites, but it feels all wrong. I can see how a viewer who had not read the original story would appreciate this relationship and this dialogue for the irony involved, for all the moments when things go unsaid. I actually like those moments too. But I was disappointed not to see the character as Christie wrote her.