While Dirty Harry was a magnificent example of fantastical Hollywood filmmaking, a story that while gloriously entertaining didn’t try and reflect the real world, Zodiac is a more grounded attempt at telling the story of a serial killer loose in San Francisco. Yes Fincher’s direction is as flamboyant as ever and yes it’s a glossy big budget movie, but with its emphasis on the minutia of detective work and with its unresolved ending, it’s a brave attempt at reflecting the reality of the case. The film doesn’t provide you with any answers – it’s a mystery that will remain as such long after the credits have rolled.

The film opens on the 4th July in 1969. Fireworks fill the sky and we see a young man take a ride in a car with an older woman. It’s an idealistic picture of America – a couple going to a diner, a nation celebrating its independence, the last summer of a great decade. But despite the fireworks and the promises of a brighter future, there’s a dark shadow looming around the corner. America’s innocence, if it ever existed, isn’t going to last long.

The attack on the two kids is a superb piece of cinema. We see them awkwardly talking as they pull up by a lake and then a car appears behind them. At first its headlights shine brightly, but then they’re turned off, adding to the unspoken menace. But then the car drives off. However, it’s not long before it returns. With the light from a flashlight shining in their eyes, they maybe think it’s a cop, but then the shadowy figure opens fire on them. It’s a senseless attack, and one that is masterfully filmed, edited and scored – I love the use of Donovan’s ‘Hurdy Gurdy Man’; it’s a psychedelic rock song, one that while seemingly upbeat and positive has a dark undercurrent to it. It works perfectly for the scene. And then after the attack we see the boy sitting outside his car, near the point of death, as the Zodiac phones the authorities to tell them of his crime. The calmness of his voice is quietly chilling, as is the way he says, ‘Good-bye’ like it’s two separate words. Here’s a person who is killing just for the thrill of it.

The second attack isn’t the grandstanding piece of cinema that the first is, but it’s equally effective. We see another young couple driving to a lake. There they encounter a masked man with a gun. He says he’s escaped from prison and the couple think they’re just going to be robbed. The young man even offers to write the masked man a cheque. But then after being tied up and after assuring his female companion that everything is going to be okay, the masked man casually stabs them. It’s shocking in how nonchalantly they’re attacked – their daytrip may consist of a picnic and kisses by the lake, but the Zodiac’s idea of fun is completely different. And there’s a great moment where after being tied up, the man asks the Zodiac if the gun was even loaded. The Zodiac then holds the gun close to his face and shows that yes it was loaded. It’s a great moment because the gun is distorted by the camera lens – it looks even larger and therefore more threatening; our lives hang by a thread and it takes very little for someone to come along and snuff us out of existence.

And it’s maybe that sort of power that the serial killer has over us that makes them so fascinating. They don’t adhere to the rules that society lays down for the rest of us. Therefore we’re amazed by them and maybe we even admire them in a perverse way. We want to hate them, but at the same we want to consume every lurid detail of their exploits and maybe even indulge in daydreams about the people we’d off if we were batshit crazy like they are. Or if we don’t have some sort of distant, guilty admiration for their utter lack of self-control, we want to at least understand them; we want an insight into their twisted soul. And of course, this hunger for answers is even more pressing when so few are made available to us.

This is why Robert Graysmith invests himself so deeply in the case. He wants to understand. He wants answers. But it says something sad about human nature when he finds a killer more fascinating than his children or his wife. Somehow we’re acknowledging that serial killers are extraordinary simply because they refuse to go along with the rest of us. They don’t create anything, they don’t expand our understanding of life and the cosmos. But because they don’t listen to the little voice in our heads that says ‘no’, they immediately become worthy of our attention.

But despite the attention that we lavish on them, what would we really find out if we could get into their heads? That they hate? That they’re mad? The answers will always be mundane, but a desire for answers will remain as long as the killer is unidentified. Wars we can understand. Natural disasters can be explained. Diseases don’t even perturb us that much because we arrogantly feel that we can do something to avoid getting them. But we need to unmask serial killers because we need the reassurance – we need to know that the person is really human, that there isn’t a supernatural demon lurking in the shadows that is going to snatch us away without warning.

The film taps into this wonderfully. Robert Graysmith’s whole quest is a quest for this reassurance. He needs to be able to look someone in the eye and know it’s them – he needs to know that it’s a mere mortal who is out there. This leads him down various dark alleys, one of which involves him going to a man’s house in order to talk to a friend of a suspect. Graysmith has a sample of what he thinks is the Zodiac’s handwriting, only to find out that the handwriting belongs to the man he’s speaking to. Graysmith is then led down into the basement where he hears the floorboards creaking above him. It’s a very creepy scene, but we’re denied any payoff. Graysmith isn’t attacked and the killer isn’t revealed. The mystery remains.

After that, Graysmith tries to bully the sister of a victim into naming the killer. He just wants an answer; he wants it to be over – briefly he doesn’t care about the truth. But then he finds out about one of the prime suspects.

Arthur Leigh Allen is the only serious suspect that the film puts forward. But at the same time we’re never told that it’s him. We only have the information that the investigation gives us, that the man was a paedophile, that he owned guns, that his timeline fitted with the Zodiac, that he blabbed important information to a fishing buddy, that his watch bears the name zodiac and that it has the crosshair logo that the Zodiac’s letters used, and that he was spotted on the weekend of one of the murders with bloody knifes in his car that were supposedly used to slaughter a chicken. But even though we have all of this information, along with tasty titbits that his freezer is full of dead squirrels and that he fucks himself in the arse with a wooden dildo, there’s still nothing concrete to tie him to the killings. Like Robert Graysmith and the detectives who investigated the case, we can only look at him and draw our own conclusions on all the circumstantial evidence. Everything screams that this is the man, but we never know for certain.

Hollywood thinking dictates that a lack of a firm resolution is deeply unsatisfying, but this most certainly isn’t the case for Zodiac. The film ends with a victim identifying Arthur Leigh Allen as his attacker, but the man can’t say for certain. And although at the end we discover that Allen died of a heart attack before he could be interviewed again, DNA evidence supposedly cleared him. A concrete answer would only turn the Zodiac into another serial killer, but without it he obtains almost mythic status. He becomes the bogeyman we all fear but which we’re fascinated by.

But although I love the mythic side to the film (ending the film with ‘Hurdy Gurdy Man’ is a master touch, reminding it as it does of the first killing and suggesting that the Zodiac might still be out there), it also works wonderfully as a police procedural. We see the bureaucracy that the detectives face and the hurdles they have to overcome in order to do their job. There’s a great little scene where the cops have to put their case forward in order to get a warrant to search Allen’s premises. Unlike Dirty Harry it’s not a simple case of finding the guy and then blowing him away.

And there’s also something quite sad in the amount of time that is dedicated to hunting this one individual (if the Zodiac was indeed one individual). Years go by, people grow older and yet the detectives are still on the case. One beautiful sequence illustrates this perfectly – we see the Trans America Pyramid being built. Everything around these people is changing as they’re hunting a phantom from the past.

However, for Anthony Edwards’ cop it all proves too much. After years he quits the case. In an understated scene we see him say goodbye to his partner with very few words expressed between the two. There are lots of emotions there, but neither can express them.

But one of the most memorable images from the film is of the detectives walking through a maze of superimposed words. No one can see the wood for the trees. Has this man killed as many people as he claims? Is he a liar who takes credit for other people’s work? Either way his campaign was a success. With the help of the media he created a myth and a mystery that hasn’t been solved, and as long as that mystery remains he’ll always be exceptional. People may want to solve the mystery, but it’ll only remain interesting while the answer is elusive.