To me there's really only one thing a filmmaker/writer should never ever do. They can use all sorts of little cheats and suspend the laws of physics for stylistic effect as much as they want, but when they use those same cheats to resolve the main mystery of the plot, then that's just too stupid. To avoid giving too much detail I'll use a hypothetical example: Suppose you're watching a suspense film and the heroine is up against the wall with killers all around her. They're armed, she isn't. She has no help and no way out, and the situation has been tensely evolving to this point for two hours. Then she just magically turns invisible and flies away with no explanation for how, when, or why she suddenly developed the ability to fly and turn invisible. The end. Good film? No. A terrible cheat. And 1st To Die is just that way. The plot's mystery is resolved by a sudden revelation that someone can do something that's impossible. Stupid, Stupid, Stupid.
Any idiot can write a good mystery if you don't have to explain how it worked within the laws of physics. Imagine the old "locked room mystery" where the victim has been killed in a room that has been locked from the inside, so how did the killer do it? If the answer is that the killer suddenly developed the ability to pass through brick walls without disturbing them, then it's not a very good mystery, is it?
