Mysteries are an odd genre. The conclusion (or "summation") of a mystery raises hob with the Hero's Journey and most other structures. Poirot's summations, for example, sometimes take a half hour. This "talking head" sequence is mitigated by flashbacks, seeing what really happened from the tec's POV, sometimes accompanied by VO narration. The flashbacks are sometimes just repeated scenes/shots rerun with the narration, and a few close-ups to emphasize certain details. The detective's arc is often shallower than typical protagonists, too. A touch of vanity (in the case of Poirot) will do. Sherlock's "flaw," a cocaine habit, was eventually dropped, with little effect on the quality of the stories. Scott, do you have any comments on the demographics for mysteries?

Jeff, not on the demographics. I can say that mystery seems to have more of a home in Hollywood as part of another genre, not a genre unto itself. So Gone Girl is a Drama-Thriller with a mystery dynamic. Unfriended is a Thriller-Mystery. Ex Machina is Science Fiction with a mystery element. But if you look at the top 50 B.O. movies from 2015, there's not one of them which you can call a straight-out Mystery. I think what McQuarrie is talking about is any sort of mystery, either big "M" (main genre) or small "m" (story dynamic). The resolution to the mystery almost always happens in Act Three. Normally a story's momentum builds and builds, so Act Three chugs along toward a Final Struggle / Resolution. To stop the action with a monologue... that is specifically what I take away from McQuarrie's tweet: If you do that, the actual narrative content of the monologue had better be damned compelling and provide a satisfying sense of conclusion. Of course, as you mention, we can use various cinematic devices to make the 'talking head' monologue more visual: flashbacks, recreations of events, voice-over narration. But if we find ourselves doing that to mask some weak dialogue, we probably haven't yet hit the right note re the story's mystery.

Thanks for the detailed reply, Scott. What I'm working on would be a Mystery-Adventure, near as I can figure. Not a lot of scare, there, but some tense traveling to and from the scene of the investigation. Thus the mystery is bookended within the adventure, and there are bigger wants that wrap around these elements like a Russian doll. I've moved much of the summation forward into a chase scene, presenting revelations as flashback during ongoing danger. Given that and the long summation sequence, it may be too complex a project for a 120 minute script. I'm looking at it in novel form now. Thanks again!