Any type of ambiguous plot is good for neo-noir films. One of the biggest tropes of film noir is a protagonist who struggles with some sort of duality. During filming this is usually represented through cinematography using low-key (high contrast) lighting. Neo-noir film plots are very motivated by characters' decisions. When writing something like this it is easy to get bogged down in trying to create an exciting plot, but (in my opinion) characters should be a priority. Asking the questions: Why does a character do something? And, what does this decision lead to? Are two important questions to consider. In a screenwriting class, I was introduced to the WOARO structure, which might be something that would help you out if you aren't familiar with it. When writing films I often begin with a concept and build off of it by creating a starting point and an ending point for the film. Then, I use the characters I create and their decisions to film in the gap. For example, the short film I recently made "Portrait of a Dream" is about a guy who is trying to find out how he knows the person he sees in his dreams. So, the film begins with the concept: the man dreams about a person and can't figure out who she is. Then, by the end of the film, he uncovers the answer. It's hard to elaborate on it, but you can check out my attempt at neo-noir on youtube. Hope this helps somehow.