Of course, this isn't the first time Poirot is on a train where someone is murdered. "The Mystery of the Blue Train" is from season 10 and stars David Suchet as Poirot, Elliot Gould, Lindsay Duncan, Bronagh Gallagher, and James D'Arcy.
In this episode, Poirot works to solve the murder of Ruth Kettering, the daughter of a wealthy industrialist. She is beaten literally beyond recognition. Added to this, in order to be closer to her lover, she changed rooms with Katherine Grey, a new heiress whom Poirot has befriended. Ruth owned the brilliant Heart of Fire ruby, which is now missing - but the safe wasn't broken into. When Grey visits her relatives, she is attacked, raising the question - did the killer have the right woman? There's gambling, adultery, broke relatives and resentment as Poirot investigates the suspects further. Lindsay Duncan as Gray's suddenly attentive cousin (she's broke) is fantastic. I had the pleasure of seeing her in person in "Private Lives," and she is a wonderful actress. Suchet as usual is the perfect Poirot. I also had the privilege of seeing him in person in "Amadeus." He truly is a chameleon. Georgina Rylance is also excellent as Katherine Gray, an insecure young woman who's just inherited a fortune and now socializes with a different class of people.
The rest of the acting, frankly, wasn't fabulous - you could spot the fake American accents right away and the characters seemed put on rather than the real thing. It might have been the dialogue, it might have been the directing - I tend to think it was the latter.
I don't remember this book, so I didn't mind whatever changes there were. I enjoyed the story.