Irritating stupidity at the end... (SPOILERS, obviously)
SPOILERS, since I'm talking about the ending.
So after all events have transpired in the house, the police is coming, they carry away the tree bodies, some of our characters are getting on a boat, some of them are walking away to their homes (like Poirot), etc, so we can have our wrap-up. But... COME ON.
Are we seriously to believe the police, happening upon this scene just ... let them all walk away? Three people died!
And for the sake of discussion, let's assume the police is perfectly content with Poirot's solution to the two initial murders. But that is as far as they should have accepted it - because that person is also dead - so... I don't know... investigate?
I mean it's ridiculous. As far as all the witnesses are concerned, Poirot exposed the killer, then the killer ran up the stairs to that roof garden / balcony area, Poirot followed her, then came back in a few minutes, saying: "Well, our killer tripped and fell to her death, so I guess we can all go home now". The witnesses not questioning that is one thing, but the police? Seriously???
Otherwise, the movie was decent, there were some details that seemed shaky (how did the kid get the blackmail money exactly without revealing himself?) - but I guess those might be clarified in the book. But this? The ending was beyond ridiculous for me that everyone just walked away. I get that from a characterisation standpoint, we needed to see Poirot "getting back into the game". But sacrificing common sense for that was not the best decision.