After Norbit, the yearís most appallingly insensitive and poorly made film about a fat woman, a geek and a Chinese person (remind us why thatís funny, someone) it might take you a few weeks to work up the courage to go back to the cinema, but there is reason to recover swiftly in Zodiac, a masterful thriller from David Fincher, director of Se7en and Panic Room.

The film addresses one of Americaís most perplexing serial killers, known as the Zodiac, who claimed to have taken 37 lives during a ten month killing spree in the late 1960s. The killer coined his name in a series of letters he sent to the San Francisco press until 1974, letters that included four cryptograms, three of which have yet to be solved. Despite a furious police investigation that spanned three decades, his identity remains unknown to this day.

The film follows Robert Graysmith (Gylenhall), cartoonist and puzzle expert for the San Francisco Chronicle, who pursued the killer obsessively for over a decade. Robert Downey Jr. delivers his best performance in years as a renegade journalist who shares Graysmithís interest in the case and Gylenhall himself handles his geeky character superbly.

Terrifying, dark and beautifully shot, Zodiac is the best serial killer film since, well, since Se7en.

Matthew Freemantle and Robert McKay

Did Zodiac require a huge amount of research, re-examining all the original evidence of the case?

- As much as possible. We have a couple of hunches. There are things you have to create or things you have to consolidate. We have discrepancies between police reports and peopleís memories of things and wherever possible, wherever we have the police report.

Is it interesting to you to explore what toll unsolved cases have on the people who investigate them?

- Well, the point of the movie is: What is justice? Is it justice knowing? Is it justice seeing them strap the guy down and stick the needle in his arm? Is it someone being lead away in handcuffs? What is the eye for an eye? What are the varying degrees? What are we prepared to accept as the end of the story? Someone once said to me, ĎYou donít have to annihilate all the rattlesnakes in the world, you just need to know where they are.í

The Zodiac killer apparently took some of his cues from movies.

- I donít know how much of that is true. I always used to question whether or not you put a movie like Se7en out and then the eighth or ninth week itís in the theatre you go to the matinee and you just arrest everyone whoís thereÖ [laughs]. Or Saw. If theyíre going to see Saw in the ninth week of the matinee itís because thereís another kind of gratification going on. Yeah, I think itíll be interesting. Itís a very different kind of portrayal of a serial killer.

Matthew Freemantle and Robert McKay