It was a mistake to advertise this version as a return to Agatha Christie's original short story. The script does jettison at least one memorable addition that was not in the original, but it also adds a great deal of extra material. Some of the material harmonizes very well with the story, and it has to do with a look, from here in the future, back at things that, during the period in which Christie was writing, were taken for granted. The indelible trauma of the First World War, the yawning gap between the haves and have-nots. The actors help sell the point that these are not just reminders of history but also reminders of human nature. The fleshing-out draws the viewer into the story more deeply than many playful or even mechanical Christie-inspired movies have done, but ultimately it wanders into territory that Christie herself, I suspect, wouldn't have entered and perhaps wouldn't even have endorsed.