From the movie Edge of Darkness, starring Mel Gibson as Detective Thomas Craven (I am no fan of Mr. Gibson, just for the record):
Darius Jedburgh: Now, you know better than anyone, cases like these are never solved. They’re simply too complicated, too much hard work. There’s a lot going on out there in this world. And you just never can connect A to B.
Thomas Craven: How do you know that?
Darius Jedburgh: Because I’m usually the guy that stops you connecting A to B. It’s part of what I do.