"I read an inexorable purpose in [Professor Moriarty's] gray eyes."-EMPT
He thought that the first time he'd ever experienced fear was that night on the moor with Henry Knight.
But that wasn't real fear. He didn't feel his stomach clench and his throat close in and the world drop from beneath his feet. What he felt on the moor was anxiety, or frustration, something trivial.
It wasn't until the rooftop, when everyone he cared for (don't be stupid, of course he cared for some people [not that he would ever admit it]) would die. He didn't really know fear until Moriarty thrust the gun into his own mouth and fired.