The character who knows too much is a classic trope of thrillers and adventure fiction. It should be obvious why-a person who knows too much is clearly going to have a much more exciting few days than a character who knows too little, or nothing at all. Here are six movie characters who probably wish they'd stayed out of it-but they didn't, so they know too much. Too much indeed!

Ben McKenna, "The Man Who Knew Too Much"

Well, it says it right there in the title. James Stewart is vacationing in India with his family when through no fault of his own he ends up hearing the words of a dying man - and not a man who died of natural causes, either. This puts him in the sights of a group of assassins who are certain he knows all about their assassination plot - and they kidnap his son to keep him from talking.

Babe Levy, "Marathon Man"

Dustin Hoffman's character in "Marathon Man" is having a terrible day. He's been captured by an evil Nazi dentist who keeps asking him again and again "is it safe?" Dr. Szell has a good reason for asking him this - Levy's secret agent brother walked a long way through New York with a knife wound in his stomach to make it to his apartment. Does Levy really expect Szell to believe that he stumbled all the way there just to die on the floor without telling him anything? Here's the joke: That's exactly what happened. Sometimes you can know too much without knowing much of anything at all.

Joe Frady, "The Parallax View"

Warren Beatty's character in the paranoid thriller "The Parallax View" has the kind of job that often leads to knowing too much - he's a newspaper reporter. And when he runs across what just might be a massive corporate conspiracy to assassinate any public official who threatens to upset the status-quo, he tries to infiltrate the organization incognito. What he learns is enough to terrify him (and the audience), but it isn't quite enough to save him if they find out what he's really about.

Harry Caul, "The Conversation"

Harry Caul is a surveillance expert - one of the best in the field. But he's got this weird hang-up about his surveillance data being used to facilitate murder. So when a seemingly innocent conversation he's hired to record begins to tweak his suspicions, he goes to lengths to protect the people involved. But just because you know too much doesn't mean you understand anything - and that's a lesson that Harry Caul learns the moderate-to-severe way.

Nora Davis, "The Girl Who Knew Too Much"

Often considered the first "giallo" thriller in movie history, "The Girl Who Knew Too Much" utilizes the common plot giallo plot point of a character who learns too much about a serial killer on the loose - and who thus becomes a target of the murderer. In Davis' case, she is dismissed by many as a "hysterical female," so she ends up having to entrap the killer herself.

Marcus Daly, "Deep Red"

From the first giallo we come to one of the best - Dario Argento's "Deep Red." Like Nora, Marcus (played by David Hemmings, familiar to the sensation of knowing too much after "Blow-Up") accidentally sees a clue to a brutal murder. But, as is often the case in Argento's films, that clue is locked away in his psyche, and he can only dig it out with a lot of exhaustive research and investigating (the targets of which often end up murdered themselves).