Falling’s just like flying except there’s a more permanent destination.

Sherlock: Why are you doing all of this?
Moriarty: It’d be so funny.
Sherlock: You don’t want money or power, not really. What is it all for?
Moriarty: I want to solve the problem. Our problem. The Final Problem. It’s going to start very soon, Sherlock. The Fall. But don’t be scared. Falling’s just like flying except there’s a more permanent destination.
Sherlock: Never liked riddles.
Moriarty: Learn to. Because I owe you a fall, Sherlock. I. O. U.