Stupidity: When Poirot's team attacks the Germans, they do it through the cover of gas they release. The Germans are having a good time chatting and not taking the situation seriously when there's a big cloud of noxious gas advancing towards them. Despite Poirot's oh-so-clever plan, they should by all means know that something is coming their way, but they get caught entirely with their pants down.
Stupidity: In the film climax, Cassie tells Justin to put his gun on the floor and walk over to her. This he does but it gives Richard the chance to grab the gun, so we can have the usual daft Hollywood ending. Why didn't she simply tell him to kick the gun over to her first to void this?
Stupidity: Harrigan leaves his partner's badge on his grave where anyone could take it and use it to impersonate a cop or abuse it in other ways. (00:50:15)
Stupidity: When she leaves him at home with a sandwich she says people will come check on him. When she gets home and he's not there, she doesn't go and ask those people where he is.
Stupidity: In the flashback about the way the victim was poisoned, it would seem that the murderer straight out went to a waitress and handed them a single chalice of poisoned champagne, ordering the waitress to give that exact glass to the victim. That's just a little bit absurd; if it's a flashback based on a testimony, the case should have been solved in 0.1 minutes once the waitress says that that very well known person asked them to bring a glass to the victim - it's a request highly unusual and that would be easily remembered. If it's just some wild guess of the detective, that's a mighty strange way to imagine how things went, rather than just the killer slipping venom in the victim's glass when they were not looking. (01:04:00)
