The construction of the film as a strictly straightforward narrative isn't just a dry, formalistic exercise, however: it's critical to underlining the manner in which information becomes available to the investigators, particularly in a world far less interlinked than our own, where basic information either isn't or can't be shared with those in nearby jurisdictions. As viewers, we're constantly trying to push at the limitations this creates - though we still have access to more information than the investigators - in trying to stitch the details together in a manner that makes satisfactory sense. We're constantly confronted, though, with the reality that our search for some kind of meaning in crimes, particularly crimes of this magnitude and visibility, may be a fool's errand; Fincher isn't trying to provide us with the kind of resolution we get in a 45-minute television episode, though the longer his film runs, the easier it is to want such neat conclusions.
As Robert Greysmith, the San Francisco Chronicle cartoonist who becomes utterly obsessed with the Zodiac case - his book provides the film's raw material - Jake Gyllenhaal delivers another dependable performance; he's particularly good at capturing Greysmith's growing mania, which excludes and even alienates everyone around him. Greysmith has an interest in puzzles himself, and the case becomes the grandest he encounters; at one point, he appears to be the only person working full-time on the case, establishing lines and linkages that have eluded others who think of the murders in isolation. It's easy to take Gyllenhaal's work for granted, not least because this is another in a line of introspective roles that conceal his broader abilities. If anything, his co-star Mark Ruffalo is even more undervalued; he breezes through light comedy in 13 Going On 30 or Just Like Heaven, but is equally capable of carrying serious fare like In the Cut (perhaps over-serious fare) and We Don't Live Here Anymore, without seeming out of his element in either context. Here he's especially good as the most upright of cops, tireless, yet absolutely by the book, stymied by the difficulties not of identifying a suspect but of bringing that suspect to justice as the law requires.
From the very first shot, Fincher establishes an acute sense of place and time that goes beyond even the datelines provided so regularly throughout the film (though it takes an attentive viewer to assess exactly when certain events take place, since the passage of time is indicated primarily with titles of the "three weeks later" variety); there's an extraordinary degree of attention to the details of décor, costume, habit and speech - there's a wonderful sequence where Gyllenhaal takes Chloé Sevigny on a date that exudes the feel of the era - but also a profound sense of a very different communications world, where the "telefax" is the latest thing, available in the big city but not in downtown Vallejo, where key sequences revolve around payphones, and where, perhaps most notably of all, the newspaper is a medium commanding the greatest of respect (by contrast, television, in the film, seems prone to farce); though much of the film takes place earlier than Watergate, this is the America of All The President's Men, and a killer with a media fixation sees no better outlet for his threats than the local quality daily.