As with all of Agatha Christie's Hercule Poirot mysteries, this one is full of intrigue and packed with mystery. It starts off with scenes from 40 years before the main story - 1896, in South Africa. This is one of those films that shows incidents well before the main plot. That is to help the audience understand something about one or more characters later. In this case, its distaste for Simeon Lee. Vernon Dobtcheff does a superb job in playing Lee as the despotic, lecherous, spiteful and mean man that he is.
Poirot gets involved with the super wealthy Lee and his family quite by chance. The radiator in his home and office building is on the blink and maintenance can't repair it until after Christmas. So, wanting to spend Christmas with the warmth of indoors, Poirot takes a call and accepts an invitation to spend the holiday at Simeon Lee's mansion.
Thus is the unfolding of "Hercule Poirot's Christmas." The only regular character who joins Poirot in this adventure is Chief Inspector Japp. It's mostly a distasteful time for the super sleuth because the majority of characters and suspects are so nasty and distasteful themselves. So, Japp's presence, besides helping with the murder mystery, is a morale booster for Poirot.
While this story has all the intrigue one expects from the pen of Agatha Christie, it also provides some hint to the audience for suspects. That's from the opening scenes and Lee's past in South Africa where he amassed his fortune in diamonds.
As with all Christie and Poirot stories, this one won't disappoint viewers but will keep one interested to the very end. It did leave me thinking that it was too bad a couple of other characters didn't get some sort of comeuppance.
Here are some favorite lines from the movie. For more dialog, see the Quotes section under this IMDb Web page of the film.
Hercule Poirot, "Ah, chief inspector. You have been thinking again. I have warned you of this before." Chief Inspector Japp, "Oh, well."
Chief Inspector Japp, "You've seen a ghost or something, Poirot?" Hercule Poirot, "Chief inspector, I might just have done precisely that."
Chief Inspector Japp, "Very violent sort of blokes, these Africans." Hercule Poirot, "Europeans do not figure too badly in the arts of violence, Chief Inspector."
Chief Inspector Japp, "Ah, but it gives you the creeps - this place, doesn't it?" Hercule Poirot, "You are too sensitive, mon ami." Japp, "That's true."