So anticlimactic

I also couldn't believe that Mark Ruffalo (or the police in general) hadn't done the same deduction that Gyllenhaal did at the end in the cafe, all he did was compare dates, letters and what they knew of Allen's whereabouts at that time, and he had it figured out. Why hadn't the cops already done this simple equation?.

I was never one to hold grudges. My father held grudges, I'll always hate him for that

***SPOILER ALERT*** (don't know how to do the blackout thingy like the guys above!!)

The police couldn't put together a complete timeline of both Allen and Zodiac as each jurisdiction had different parts of the puzzle that were not shared between them. Graysmith's research concludes information from each jurisdiction and thus completing the timelines of both Allen and Zodiac for complete comparison.
I think it's a wonderful film, especially on a second viewing as when Allen is questioned you know it's him! and the tension is unbearable as you know they have to let him go as it's all circumstantial. The police departments at the time are ill-equips in the sharing of evidence across jurisdictions, communication is minimal and the newspapers print everything that all jurisdictions receive without each of the departments communicating and thus giving a much deeper, contorted and confusing number of facts. Zodiac used the press to hide his actions by confessing to murders he hadn't even committed jumbling up all the evidence and at the same time goading the police into making poor decisions, rushing to ill conceived evidence and really just getting into a terrible mess! It makes me think that by the end of the 60s definitely by the end of the 70s if they had all sat down at a table and gone through all the evidence together they would have come to the same conclusion the Graysmuith comes to.
The movie could have ended up going down the 'Silence of the Lambs' route and made up a fictional ending where Graysmuith is in the basement of the killer and an attack ensues ala Buffalo Bill - Clarisse Starling and I bet the studio wanted that too! So good for David Fincher..... Anyway that's my take on the events. Cheers x

Graysmith is convinced it's Allen. In that sense, the movie is an "accurate" take on the source material. There's simply not enough convincing evidence to tie ALA to the crimes.

The movie's ending is anti-climactic, but I like that about it. Real life is often that way.

What did you expect from a movies based on theories and investigations of other people about a case that has never been completely solved and probably never will?

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The movie is garbage and totally based on lies, and the Allen guy was disqualified by DNA evidence. You twist the truth to give good fiction, not an anticlimactic thing like you say.

Incorrect. Zodiac is a masterpiece and the ending is quite fitting.