What Makes A Good Noir Film?

There is a genre in films that is incased with darkness and mystery, one that also has no actual definition surprisingly. Today we take a look at films that embraced the nature of crime in a style that oftentimes relied on black and white and grittiness but more so creating sub-genres that created such a unique style. As always we wanna know what murder you were able to solve as we ask, what makes a good noir film.