One of the worst things that can happen when you're watching a film is for a legitimately interesting character to suddenly disappear with no explanation. One minute they're there, part of the plot and serving as key motivation for the main player and then whoosh... gone, just like that.
The film, and the other characters, just don't mention them ever again. It doesn't make any sense. How does a film-maker completely lose track of an actor? Of all the things that should be high priority, keeping tabs on characters is certainly up there.
And it's not just amateur directors who are guilty, either - I'm talking about the likes of Steven Spielberg and Ridley Scott, masterful film-makers who should know a lot better. Regardless as to whether or not there's any external explanation, it makes for an incredibly frustrating viewing experience. Plot ambiguity can be effective, but getting audiences invested in someone only to needlessly forget them is annoying especially when they're being played by a famous, well-known performer.
Here are nine of the most seriously baffling examples...