There's an inherent shagginess to nearly all dramatic narratives based on true stories, and I keep rethinking how it turns this one into one giant paradox. Fictional serial killers are usually based off cases like this one - the idea of a killer who names himself, sends elaborately creepy letters, and plays games with the media is the sort of thing that happens all the time on NCIS. But paradoxically, it's so fascinating and borderline predictable in fiction because it almost never happens in real life. The Zodiac case is so compelling because it is a mix of horrifying, cinematic artifice and the brutal reality of bureaucracy and unsatisfying answers. It's like two movies at once: how can the same world where a man sends ciphers to three newsrooms and threatens that he'll kill a school bus of children if they're not printed also be one where the investigation is held up because one county doesn't have a fax machine? The first one isn't ever supposed to happen in the real world, and the second happens every single day. It's this paradox that drives the characters to madness, but it also maddens any attempt to dramatize it. Sure, you can make a film about ambiguity, a hunt for answers with no answers, but how do you deal with the unresolved ambiguity of the people doing the hunting? In fiction, friendships formed solving these kinds of cases turn into unbreakable bonds, and people who become significant figures each other's lives usually stay that way indefinitely. In real life, sometimes friendships just fade for no real reason, and sometimes people's addictions just get worse and they get mean. But how do you reconcile the two when RDJ's Paul Avery spends the first half of the film bonding with Gyllenhaal's Robert Graysmith, the only person who really understands him and feeds his hunt for answers, and then abruptly disappears in the second half and denounces the case as his alcoholism escalates offscreen? The easy answer is "human behavior", and in a film that was just about their friendship, there might be more nuanced room to explore that. But this is a film about the Zodiac case, one that already has a titanic runtime, so there's no time to explore why Avery falls off the map: he just disappears. Life just happens. And that's the alternating frustration and elation of this film: it revels in unanswered questions, not only because it thematically wants to, but because it narratively has to. It's the core of what makes the film so creepy and enduring, the lingering knowledge that the cinematic dramatics onscreen actually happened in a neighborhood that looks like yours, and that the distinctly un-cinematic human complexities actually happened, too - and those complicated people were in charge of solving this thing. The thesis is that you'll never get catharsis even when it feels most earned, that humans will be humans, even when the circumstances feel unreal: maybe that no one is ever really in charge, and everyone's always on the edge of losing it, and no one will ever really be able to explain why.