John once heard Moriarty threaten to burn Sherlock. That statement had told John just how little the man knew the world's only Consulting Detective. Oh, he could talk a big talk, but in reality he was totally clueless.
Sherlock is always burning. Always.
His mind is constantly lit up and lit out with knowledge and information and sheer, undeniable brilliance. His passion for his work, for the grime and grit of London under his nails, and the thrill of the chase radiates through his skin, seeping out of his pores, permeating anything and everything around him.
Oh, yes. He burns. He burns so brightly that sometimes it physically hurts John to look at him, like staring straight at the sun or watching a flash grenade go off without shielding your eyes. It is both beautiful and terrifying in its intensity and makes him want to do nothing more than to stare and stare and stare, his whole body screaming at him not to glance away, even for a moment, least that fire go out and leave him shrouded in darkness.
There are times when Sherlock draws him in, moth to flame, and before he knows it he's burning up with fever. His hands trail along John's body, nigh flaying his skin from his bones, mouth like molten lava flowing along the curve of his spine, until he feels he's about to spontaneously combust, go supernova, and die from all the love in his heart.
There are other times Sherlock burns, but more softly, and the harsh glare of that bright white brilliance morphs into a gentle glow; like a star twinkling on the horizon, guiding him across the misty seas towards the safety of a distant harbor, whispering: Safe. Safe. Home.
He is the Northern Star of John's heart and, like any Captain worth his salt, John will set his course by him and follow it diligently. To the ends of the earth if need be.
No. Jim Moriarty knows nothing about Sherlock Holmes.
He's a man of darkness.
He knows nothing about the light.