John Anderton: Any contractions?
Casey: Only the ones you give me.
Agatha: Murder.
Wally the Caretaker: I like you chief, you've always been nice to me. I'll give you two minutes before I hit the alarm.
John Anderton: Why'd you catch that?
Danny Witwer: Because it was going to fall.
John Anderton: You're certain?
Danny Witwer: Yeah.
John Anderton: But it didn't fall. You caught it. The fact that you prevented it from happening doesn't change the fact that it was going to happen.
John Anderton: Why don't you cut the cute act, Danny boy, and tell me what it is you're looking for?
Danny Witwer: Flaws.
John Anderton: There hasn't been a murder in six years. There's nothing wrong with this system it is.
Danny Witwer: Perfect I agree, but there's a flaw. It's human.
Chosen answer: It's what's known as a McGuffin; a plot element that seems to be important when introduced, but serves no purpose other than to intrigue/distract the audience. The term was popularised by Alfred Hitchcock.
J I Cohen
That's not *quite* what a MacGuffin is. A MacGuffin not only seems important, it *is* important; in fact, one of its two diagnostic characteristics is that a MacGuffin is something around which the entire plot revolves. The other property fundamental to what makes something a MacGuffin is the fact that the origin, purpose, function, and, in some cases, even identity of the object is left either vague or completely undefined. The briefcase in Pulp Fiction is a classic example (although there *is* a compelling argument that the object in the briefcase is in fact a specific artifact).
Well, according to the doctor when the operation is beginning, the doctor reveals that in prison, he spent all of his time in the library, including books on medicine and technology. As a result, he found his "true calling", and is thankful to John for helping him see that.