Sherlock does not find himself in situations where he is truly afraid.
Being kidnapped is...disconcerting to say the least, but he never feels fear.
Real, bone-shaking terror that sets your teeth on edge and strips away all logic unit nothing is controlling you except the fear.
That is not to say he has never been scared before. Though even then the feeling is fairly uncommon.
He hadn't felt fear when he was beat up at school.
He hadn't felt fear when he woke up in a strange house with no memory of the past two days.
He hadn't felt fear when he was mugged and left for dead in an alley.
He hadn't felt fear when he was standing across from John at The Pool.
He hadn't felt fear when he was threatened by Moriarty.
But that smile. His smile. The smile that taunted and taunted him day in and day out until he could hardly think, that mocked him constantly, was enough to drive the sociopath over the edge.
'I made you care...'
Warm and Soft and Gentle replaced by Cold and Sharp and Hard.
'You are such a fool...'
Familiar blue eyes that ripped his chest open and burnt his heart out.
'It was pathetically easy. Really, do you think anyone actually cares about you?'
The mannerisms, the quirks, heck even the limp had disappeared and a stranger waltzed through that door.
'Tell me, Sherlock. Did you suspect, even once, that you were being deceived?'
It wasn't a gun that held Sherlock firmly in place but it was a horrible mix of shock, disbelief and pain.
' I so look forward to the next time we meet Sherlock...'
He flinched at the hate and disdain that dripped off of his name.
'...they say pride comes before a fall. And you are so very, very proud Sherlock. I think I'll enjoy hearing you beg for death the most.'
And for the first time in his entire life, staring into the face of both a complete stranger and close companion, Sherlock Holmes felt real fear.
Sebastian Moran simply...smiled.