Do It

"Slay the Dragon"

Sherlock didn't even think.

His body moved without the consent of his brain, immediately pointing the gun at the older brother.

He snapped his eyes up, shocked by his own actions.

Mycroft, for his part, didn't look surprised.

His own ice-blue eyes were filled with something that tightened the knot around the detective's neck.

Acceptance.

"Holmes kills Holmes..." Jim Moriarty's voice echoed, it's tone cheerful and upbeat.

The younger man sneered at the recording of his archenemy.

He opened his mouth to protest, to say that he would never... But Mycroft hushed him with just two words.

"Do it."

The detective's eyes snapped back to the red-haired man he called "brother".

"...What?" He asked, lowering the gun from where it was pointing at the fox-haired man.

But Mycroft was already moving, stepping up to him in record time and pressing the barrel of the gun firmly against his own heart, a warm hand covering Sherlock's.

The detective was so shocked he could only stare at his older sibling in horror.

"It's what we've both been waiting for, isn't it?" The rumble of his voice vibrated against the gun, as he talked. "So go on." He tightened his grip on Sherlock's trigger finger, willing the younger to press it. "Pull the trigger, Sherlock."

The detective stood there, frozen, looking like a scared deer in the headlights.

He couldn't believe this was happening...

'Why am I not afraid?' That question was being pushed to forefront of his mind by the Mycroft that lived in his Mind Palace, demanding he paid attention, but for once, the detective couldn't focus.

This was all happening too fast...

"Sherlock don't do it!" John. John was still there... They forgot about Watson. "Damn it! Let go of that gun, the both of you!"

But all the younger Holmes could focus on was the steady rhythm of Mycroft's heart, as it gently pushed the gun back and forth with the force of it's beats.

This pulled him back to a time long past, when as a little boy he would sneak into his older brother's room when awoken by a nightmare. Seeking comfort in this strong, steady sound that never faltered, no matter the weather outside, and chased all the monsters away.

Just like all those years ago, it was calm.

Beating the same slow and steady rhythm, it always did.

'Why am I not afraid?'

There it is again, that infuriating question Sherlock didn't want to know the answer to.

But the detective was forced to listen to it now.

'Why is he not afraid, indeed...'

Sherlock closed his eyes for a second, though it felt like hours, and allowed himself to be engulfed by his Mind Palace.

He began to think, to analyze, to remember.

Even when faced with the possibility of death, of fratricide, Mycroft's heartbeat didn't speed up.

Normally that would scream of the person's unique ability to control his body, something that takes years of discipline and practice to achieve...

'You know that is not the correct answer, Sherlock.' Inner-Mycroft scolded gently, cutting him off and forcing the younger Holmes to think in a different way. 'Focus, brother-dear.'