Zodiac probably shouldn’t be a movie.

By all metrics - conventional wisdom, storytelling norms, the film business, what audiences want to see - there is nothing traditionally appealing about Zodiac. It is a nearly three-hour film featuring a murderer who kills five people - two before the movie starts - in the span of ten months (and in the movie, in the span of 25 minutes). He then writes a series of letters to local newspapers for a few years. Then he disappears. The police run down lead after lead, but achieve no resolution. The killer is never caught. It is perhaps as uncinematic a true crime story as you could conjure.

But in the hands of David Fincher, the story of the Zodiac Killer and the men who pursued him is not only cinematic - it's the crowning achievement of the director's career, a masterwork stubbornly faithful to its source material even while transcending it. Ten years on, 2007’s Zodiac is a bona fide classic, a borderline autobiographical examination of obsession to detail and a meta refutation of the director’s most popular film. It’s a document of not only the events it's depicting, but also - despite its director’s protestations - of the period in which the film was made.

Dumped in March by studios and ignored at the box office, Zodiac initially seemed to prove the conventional wisdom correct. As Fincher would observe in an interview later that year, “in retrospect you look at it and say maybe audiences who are looking for entertainment on a Friday night don’t want that toll taken on them.” Zodiac nevertheless began growing its cult almost immediately. By the end of 2007, many film critics and bloggers had it as Top Ten material - and that’s in a year that gave us There Will Be Blood, No Country For Old Men and The Assassination of Jesse James By The Coward Robert Ford. Today the film is at #12 on the BBC’s Best Films Of The 21st Century. And over the past decade the movie has ripened into something special indeed: a film that hews frustratingly close to the real-life facts that inspired it, with a cast that was about to explode in several different directions, made in maybe the last year it could have been.

Though Fincher knew of the Zodiac case since his own childhood, as a filmmaker he comes at it here like an enthusiastic, recent convert, dying to tell you every fact of the case, afraid to leave anything out. It makes him a kindred spirit with Robert Graysmith (Jake Gyllenhaal), the newspaper cartoonist who is consumed by the case over a decade in the film. And Fincher’s attention to every mundane detail of the case is of a piece with the film’s detectives, quietly and calmly giving equal weight to both concrete evidence and to the leads which, after exhaustive investigation, don’t pan out.

Fincher is also obsessed with detailing just how slow and imperfect real police work can be. In 2007, this was an exciting shift for the filmmaker, whose previous serial killer film a dozen years prior featured policemen whose luck and preternatural skill at sniffing out clues border on the magical. If Brian De Palma's CV is, as is often stated, that director’s conversation with Hitchcock, Fincher’s Zodiac feels like a conversation with himself - the Fincher who made Seven twelve years earlier. Seven made serial murder exciting, a lushly designed horrorshow, coloring a genre for years to come. Zodiac’s cops are terminally ordinary, frustrated, human. Zodiac’s murders are banal and unsexy. Hunting its killer is dreary, unsatisfying work.

Fincher opens his film with period-accurate Paramount and WB logos to, as he says on the film’s commentary, “set the analog scene” of 1969, and a first-time viewer will come to understand over the next two hours and 42 minutes how crucial that distinction is. This was a world quite removed from that of 2007; ten more years have done little to reduce one’s wide-eyed disbelief at how ancient the investigative technology of 1971 feels. As the film’s protagonists wade through this low-fi molasses - two police departments struggle to share evidence (“we don’t have a fax.” “We don’t have a fax either.”), and one department isn’t even aware that a third jurisdiction is involved - 2007 audiences can actually feel the Zodiac slipping through the fingers of the men hunting him.

Ten more years of information tech and DNA science have only sharpened the ache of the technological limitations Fincher depicts. Inter-jurisdictional cooperation - something that stymied the Jack the Ripper investigation a century earlier - is further hampered here by the limits of how (and how quickly) the departments can and can’t share information. Search warrants don’t get signed within hours; they take thirteen months. It’s frustrating to watch, and that’s the point. “Try living with the case for decades,” Fincher seems to suggest.

Zodiac has been cited by both admirers and detractors as being nothing beyond the depiction of details; "the details are the story," Fincher insists. Well, sure. But detail after detail after detail pile up in the film’s near three hours. And the effect of spending years hopelessly lost in those facts - living for the endorphin splash of learning a new, possibly game-changing detail, or the elevator drop in your gut of spending way too much time on the wrong clue - is the film’s genius.

When a newspaper leak prompts an explosion of “tips,” SFPD homicide inspectors Toschi and Armstrong (Mark Ruffalo and Anthony Edwards) wade through eight months of concerned citizens trying to turn in their friends, lovers and neighbors (via a snappy, kind of hilarious montage) before landing on the highly suspicious, thoroughly creepy Arthur Leigh Allen (John Carroll Lynch). In an electrifying scene police question Allen, who volunteers details that weren’t made public, and whose behavior and demeanor send them out of the interrogation almost certain he’s their man. Almost. Fincher coached Lynch to play the scene as upset and innocent, while every word out of his mouth was damning. The effect is to put us in the investigators’ shoes. We know he’s the killer in that moment; we fucking KNOW it. But soon after, new evidence tells us it’s not him. Whatever case is made for Allen as the killer, the facts won’t cooperate. Ever.

And that's what Zodiac is about - looking at someone you're almost sure is guilty, while holding yourself to a process that does not allow "hunches" into evidence. Do you decide to let this conflict eat up your finite time on earth, or do you tell yourself that the evidence doesn’t support your gut feeling, so your instincts must be wrong? That quiet life sentence is at the heart of the film. Fincher took a book that was actually titled Zodiac Unmasked because it was so sure of its conclusion...and he inserted 5% doubt in it. And he made a film about living with that 5% doubt. Zodiac isn’t just about an itch you can’t scratch; it’s the dawning awareness that the itch will never be scratched. In the acknowledgement of that itch, in this film that James Ellroy calls “an epic of unknowability,” Fincher presents those who choose to live with that itch as a certain kind of uncelebrated, cursed hero. “Just because you can’t prove it doesn’t mean it’s not true,” Graysmith tells Toschi. Easy enough for a newspaper cartoonist to say, but it’s a mantra that’s not available to a cop. Toschi must live with - and maybe even convince himself of - the uncertainty.

It’s tempting to compare the film to Pakula’s All the President’s Men, and that film is without question a touchstone for this one in many ways. Aesthetically and narratively, All the President’s Men is peeking around more than a few corners of the San Francisco Chronicle’s newsroom shown here. But if Zodiac is a successor to that film, it’s a nightmarish alternate: Woodward and Bernstein obsessively pursued truth and justice - and they got it. The men of Zodiac are denied that closure, to this day. And in that regard, Zodiac is not a paean to ‘70s paranoia; it’s an ode to the confusion of the ‘00s, presented via a period film. The 2000s were, for many of us, the decade where we learned just how much we don’t know. A bombing in New York by Al-Qaeda justifying a war in Iraq, over WMDs that didn’t exist. Deprived of facts, people got antsy for closure, even if that closure came in the unrelated form of Saddam Hussein hanging from a rope. Get enough people running around with no facts, and the truth becomes a pipe dream. As such, Fincher’s period film doubles as a digital snowglobe of ‘00s America.

Adding to the film’s time capsule vibe is its cast, one that would be scattered across the cinematic landscape almost immediately after wrapping this film. The next summer, Robert Downey Jr. (who plays journalist Paul Avery) would be launching the Marvel Cinematic Universe (and more or less staying there). Mark Ruffalo would join him a few years later. Both are exceptional here, presenting two sides of an obsessive coin. For all his snark and sarcasm, Avery lets the Zodiac case get under his skin, where it poisons him from the inside, and Downey plays that spiral quite well.

Inspector Dave Toschi is a new kind of hero, one who lives with a mystery he knows he will likely never solve, suffering in quiet dignity as he watches Dirty Harry put his case to bed in two hours on the big screen. Ruffalo plays Toschi with warmth and resignation. Though Bullitt and Dirty Harry are in part based on the guy, the bow-tied Toschi resists his own mythologizing, giving us the true, unexciting (and unexcited) face of diligent, real police work.

Toschi’s partner Bill Armstrong is no less a hero, showing up day after day to confront the worst of humanity with kindness - not just for the citizens he’s sworn to protect and serve, but for his partner Toschi who, unlike Armstrong, can’t quite compartmentalize or, more tragically, tap out when he’s had enough. Edwards is stealthily spectacular here, further personifying Fincher’s refutation of the “two-fisted men of results” movie cop stereotype.

Jake Gyllenhaal was often cited in 2007 as the weak link of the cast; folks online wondered how much better someone like Ryan Gosling or Edward Norton would have done in the role of Robert Graysmith. For this viewer, a 2017 viewing silences those armchair casting directors. Looking at Gyllenhaal in Zodiac through the prism of today, it becomes clear that folks were reacting to not a performance, but what was intentionally written as a kind of dopey character. It’s unlikely that Fincher would hang his film on the shoulders of an actor who wasn’t up to the task. This is the Graysmith that Gyllenhaal and Fincher wanted on the screen. Graysmith, the film argues, is the kind of not-terribly-endearing oddball that maybe we need to be tenacious and vigilant on cases like this. (As screenwriter James Vanderbilt notes, “obsessive people are the ones who keep us safe.”) Moreover, he’s an important audience avatar. Toschi and Armstrong are shackled to facts and they both know better than to get emotional about their work. But Graysmith is high-strung and caught up. His confirmation bias is almost certainly an investigative flaw but Fincher shows, using ourselves as his subjects, just how someone can get caught up in that kind of bias.

Fincher has publicly rejected the idea that his film is a commentary on post-9/11 America. That’s all well and good, but maybe five and a half years after the September 11 attacks, Fincher couldn’t see - or maybe couldn’t even know - how much the film reflected the country during this period. In the months following 9/11, people liked to say kind of trite things about how important it was to live our lives, to not change our daily behavior. “Otherwise, the terrorists win.” Or, as the Zodiac poster tagline said, "there's more than one way to lose your life to a killer." Maybe it’s easier to spot today, but it’s tough to look at TSA airport procedure, Homeland Security safety measures both within and without the Patriot Act, and an increasingly Draconian immigration policy and not think, “the terrorists won.” Zodiac follows a group of individuals who literally changed the way they lived their lives, profoundly and permanently, as a result of the Zodiac’s crimes (and, perhaps more notably, his letter-writing campaign of terror). Dave Toschi is 85 years old now, and every year he still visits the intersection where cab driver Paul Stine, the Zodiac’s last confirmed victim, was murdered. Toschi sits in his car on that corner, cursed with the knowledge that he doesn’t have access to every page of a story he’s condemned to read over and over.

Near the end of Zodiac, Robert Graysmith, as certain as he can be of Arthur Leigh Allen’s guilt, makes a declaration. “I need to stand there and look him in the eye and know that it’s him.” The movie, in its final moments, tries to grant Graysmith this wish, as he and Allen stare one another down in an Ace hardware store in 1983. There’s every reason to think that this scene is giving Graysmith that certainty he needs, a triumphant validation, if only for himself. But when we’ve spent 162 minutes poking holes in that certainty and undermining it at nearly every turn, you can look into Gyllenhaal’s eyes, and see that his knowing nod might mean something else entirely: that even there, in that moment, the certainty is eluding him. The nod might be intended to provide closure to a dissatisfied audience, or maybe a nervous studio. But the mess of uncooperative evidence and what we know of the real world tell us his nod might be a resignation - I will never know. I am goddamned to never really know. The terrorist won.