"He'd kill us if he got the chance."
San Francisco's Union Square. We're on top of a building, looking down into the bustle. Jazz plays, punctuated by weird electronic pops, clicks and warbles.
Slowly, we zoom in on the action, picking out a dozen little stories playing out in the crowd. A panhandler, a couple walking their dog, a mime annoying a shabby-looking gent in a raincoat, mimicking his actions.
Any one of the actions could be important, but we're not sure who to follow. It's only as the camera homes in on one detail that the important element becomes clear. But what are we missing?
That's the conundrum facing Gene Hackman's Harry Caul, the surveillance expert at the heart of The Conversation. The aforementioned shabby raincoated chap, he's an unassuming figure – easily overlooked.
He's a cold fish, cutting himself off from any emotional ties for fear of what they might reveal about himself; his only passion is his saxophone.
Caul's haunted by a past case where his inaction led to a tragedy – so it's not surprising that he becomes obsessed with a single phrase in a conversation. The exchange, between two people he's been hired to follow, seems to suggest that they will be murdered by his employer – so Caul picks over it again and again, searching for the hidden meaning in their words.
Inspired by Michelangelo Antonioni's Blow-Up – in which a photographer becomes obsessed by a detail in one of his pictures – The Conversation's focus on surveillance places it firmly alongside paranoid conspiracy thrillers of the 1970s such as The Parallax View, Klute and Chinatown.
Keep your eyes peeled for performaces from frequent Coppola collaborators Robert Duvall and Harrison Ford, both here playing oily corporate authority figures straight out of the Nixonian mould.
Although it was in production long before the Watergate scandal broke, The Conversation's focus on surveillance technology meant that it tapped into a zeitgeist in America, reflecting people's concerns over the dehumanising aspects of technology.
Having cut himself off from the consequences of his actions for so long, Harry's attempts to do the right thing ultimately lead to tragedy – but not the one he was expecting.
For tech fans, The Conversation is a feast. As well as the Watergate-era surveillance tech featured in the narrative, Coppola used plenty of innovations in making the film. That long opening shot was achieved with a programmable servo lens, created specially for Coppola, while the film's extraordinary sound design was the work of editor extraordinaire Walter Murch, whose space-age soundscapes formed the backbone of George Lucas' THX-1138.
A technically brilliant exploration of the themes of alienation, the destruction of privacy and voyeurism, The Conversation is still very relevant in today's share-it-all culture. It's surely only a matter of time before there's a remake in which someone becomes obsessed with the nuances of a 140-character message…