In the last of this series, we will consider arena. Many writers believe erroneously that arena is solely the remit of the Director or Director of Photography, but this belief relies solely on the idea that arena is *only* about "what we see as image" or the location.
Arena is not just about image or the location of your story, but its whole world - "the feel of the piece". In creating your Thriller's "story world" like this, you may consider storytelling devices like non-linearity, voiceover or montage; mise-en-scene, allusion or motif. There are no "right or wrong" ways to approach arena per se; instead arena relies on consistency and context.
Consider the nightmarescape that is the arena of Se7en for approximately 80% of the movie. It frequently rains, thunder overhead; neon signs from strip clubs and food franchises mirror in the puddles on the ground. But it goes *beyond* grotty and horrible: this place is HELL, "abandon all hope ye who enter here." Mills has moved to the city to pursue a promising police career: he knows in this horrible place, there are the "ultimate" bad guys and he can rise through the ranks quickly. His Wife is not so lucky; she *was* a school teacher, but has no job now - perhaps intimating children have no place in this vile City. The City is a horrifying place, a conurbation so dark and twisted Mill's Wife, newly pregnant herself, cannot even imagine raising a child there to the point she tells Somerset first, asking for advice on whether she should seek an abortion.
But remember, John Doe does not choose this hellish place for the final showdown between him and Mills; instead he makes his terrible last confession to Mills' repeated demands - "What's in the box?" - in the middle of an open field, in bright sunshine - the strangest of contrasts. But then, Se7en has one of the most famous "downer" endings of Thriller movies: the audience expects Mills and Somerset to be triumphant and Doe to be vanquished. Instead, John Doe gets what he wants: death, with Mills' career ruined and his Wife dead. Somerset, having wanted to go into retirement with his head held high, instead is tormented by the proceedings that unfurled in front of him, which he was powerless to stop. In short, the good guys lose and the bad guy Doe (even though he dies), wins.
Notice from the above then, the arena takes in the story and RELATES IT to image and location. For the screenwriter, the vile, dark city gives Mills, his Wife and Somerset motivation for the way they look at the world and react to it. John Doe, a clever and manipulative man, takes advantage of Somerset and Mills, taking them somewhere seemingly innocent in the resolution - then blowing them away with his final revelation.
Using arena in this way makes the screenwriter's work better, but crucially does not do the Director or DoP's jobs for them, since they are still able to render that arena as image in the way they see fit. If story is the "job" of the writer, it makes sense to use ALL of its arsenal, rather than leaving arena out and concentrating instead on say, dialogue (as is so often the case in spec scripts).
Deviation has a very strong arena - and not just because its writer JK Amalou is also its director. Shot in our capital city, JK wanted to bring forth the "kind" of London audiences just don't see in Brit movies on average. Amber's car journey with her abductor Frankie is a "Road to Hell", bringing forth huge, dark, nightmarish vistas, crucially unlike the smaller, more "underground" dark minutiae "behind closed doors" called forth in the likes of Se7en.
So if you're writing a Thriller, best of luck!