Here is a good review if you are interested:
http://www.pajiba.com/pajiba_blockbusters/the-conversation-review.phpFrom the review:
The film focuses on Harry Caul (Gene Hackman), a surveillance expert hired by an executive (Robert Duvall) to record his wife’s (Cindy Williams) conversations with her possible lover (Frederic Forrest). Caul is great at his job, assembling a master recording from separate microphones in a crowded San Francisco plaza, so perfectly captured by the film’s masterful opening sequences. Yet, Caul’s mastery of surveillance does not translate into a mastery of security. While he prides himself on being able to keep his life private, we watch as he continually fails to do so: Caul allows himself to be bugged by his professional rival, his triple-locked apartment is easily accessed by his landlord, and his equipment is stolen. Yet, despite Caul’s incompetence when it comes to his securing his life, the film posits that his chief weakness is the fact that he is a moral man doing immoral work.