10 Most Disturbing Plot Twists In Non-Horror Movies

"He'd kill us if he had the chance."

These are the words that haunt veteran surveillance expert Harry Caul (Gene Hackman) throughout Francis Ford Coppola's paranoid thriller The Conversation. Caul picked up these words from a man who was having an affair with the wife of Caul's wealthy employer (Robert Duvall), who hired Caul to record the pair during one of their meetings.

Armed with these words and haunted by a past assignment that led to an avoidable murder, Caul tries to keep the tapes hidden, but is eventually forced to give them up by his client's assistant (Harrison Ford).

Sure that the couple's time is now numbered, Caul tracks them down and is forced to hear them being murdered by his vengeful client. Enraged, he races to confront him, only to learn that it's the client who was killed, not his wife or her lover.

Listening to the tapes again, it becomes clear Caul misheard the words that have been torturing him, as the recording actually says: "He'd kill us if he had the chance." This whole time, he'd been listening to a murder plot.

Worse still, he's then threatened by his client's assistant to stay out of the situation, and threatens him by saying: "We'll be listening." Caul tears up his apartment, looking for a bug, but fails, and the film ends with his life ruined and his paranoia overflowing, as he casually sits and plays some jazz on his saxophone.