Not only did Fincher create one of the seminal crime procedurals of the late 20th century in Se7en—a film that is generally considered to have redefined the look and tone of both the crime and horror genres ever since—he then went ahead and followed it up just over a decade later with one of the definitive entries in the sub-genre to date. Rather than try to replicate or outdo the morbid, gritty mood of his inventive sophomore effort, he turned his attention instead to a very real and mysterious case—one that has befuddled investigators and researchers for decades, and which to this day remains unsolved.

Not that Zodiac is any less macabre. While it may dial down the sheer quantity of graphic gore and violence that made Se7en so shocking—in favour of a heavier focus on the investigative procedure itself—there remains the same oppressive bleakness that occupies every second of its runtime, along with a sense of jaded disillusionment that corrodes the minds of its protagonists. One by one the three leads here get worn down by their exhaustive efforts to try and pin down the killer—a police detective, who grows increasingly frustrated by the endless dead ends and red herrings that the case throws up, as well as a lack of any physical evidence to corroborate his suspicions; a crime reporter, who ends up so embroiled in the ongoing investigation that it turns him into a paranoid delusional who resorts to drugs and alcohol to provide some form of reprieve; and an amateur enthusiast, who becomes so fixated with the killer, clinging onto the vaguest strands of evidence and pursuing any untapped avenue that he can find, that it occupies every waking hour of his day, taking precedence over all other aspects of his life.

Though the Zodiac’s identity is strongly inferred at the end, in truth, within the context of the film it’s of very little consequence, because by this point he has destroyed so many lives over so many years—both those of his victims and their families, and those of the people trying to catch him—that there really is no catharsis to be had for anyone involved. By the end the film has become far less concerned about trying to pinpoint who the killer might be; instead its chief interest lies with the people left behind—demoralised by an all-consuming, single-minded pursuit that has completely shattered their resolve.