The plot revolves around surveillance specialist, Harry Caul (Gene Hackman), hired to record a couple’s conversation. He faces a crisis of conscience when he suspects that the couple is having an affair and that handing his client (the woman’s jealous husband) the tape could lead to the two targets’ murders. As he starts to try and figure out how to save the couple, slowly the watcher becomes the watched as Caul suspects he too is in danger.
So in obvious ways, the film’s about the perils of surveillance. But more crucially, it’s about the perils of the mindset that enables surveillance. At the beginning of the movie, Caul sees people solely as sources of information. As he says in the opening sequence—while he’s spying on the couple—“I don’t care what they’re talking about. All I want is a nice, fat recording.” His professional philosophy is captured by lines like “I don’t know anything about human nature … That’s not part of what I do” and “What [the clients] do with the tapes is their own business.” Lives aren’t lives to him; they’re mere sound waves on tapes, to be packaged and passed off to someone else.
That changes when he fixes a distorted part of his recording, and hears the man saying to the woman, “He’ll kill us if he gets the chance.” Caul realizes the “he” is his client, and in that moment his earlier worldview inverts: Caul no longer cares about the big, fat recording, he cares about what the couple are talking about. With time, the words spooling away in his tape decks gain significance to him. He combs through the recorded conversation, attempting to understand the man’s and woman’s feelings and fears, to glean any insights that could help save them.
In this, Caul fails. It wasn’t the couple that was in danger, it turns out. It was his client. Caul’s lack of experience, intuition, and insights about “human nature” makes him misinterpret what he hears, a fact the movie highlights by using a different line reading of “He’d kill us if he got he chance” after he realizes the client has been killed. The emphasis shifts from “He’d kill us,” to “He’d kill us.” In that moment, as editor Walter Murch says in Gene D. Phillips’ Godfather: The Intimate Francis Ford Coppola, “Harry [Caul] hears the line in his mind as it must have been all along.” The truth was always there. Caul just couldn’t hear it, because understanding how voices have inflections, and how inflections convey emotion and truth, was never part of his job.
You can see the present-day lessons here pretty clearly. The hardest thing to believe about the National Security Agency’s invasion of millions of emails and phone calls wasn’t that the agents did what they did. Big Brother Cinema prepared us for that. It’s how thoughtlessly they did it, how little regard they showed for the human beings whose information they were taking. How could PRISM so matter-of-factly request all of Verizon Communications’ customers’ phone call information? Seize over half a million email address books in a single day? See one of its members draw a self-satisfied smiley face on a slide that illustrated how the NSA had circumvented Google’s encryptions? It all seems to stem from the very thing The Conversation warns us about: how easy it is to turn people into faceless ones and zeroes.