Author's Note: I started this fic a couple of weeks ago, before the events at SDCC started the rumor mill going into overdrive. I'm a massive fan of Tom Hiddleston, and having him on Sherlock would be my dream come true. So this is my take on what an episode about the elusive third brother could look like. I hope I'm doing the Sherlock characters justice, I watch the show (and did a complete re-watch of all the eps in preparation for this) but I have not yet been dabbling in the fandom. The fic is complete so updates will come regularly every other day as I polish up the chapters. Thanks to my good friend Lizzieanne for being my sounding board and proof reader.

Introduction

It was a typical London November evening. A persistent drizzle fell from the lead grey sky, slowly but surely creeping through John Watson's jacket as he walked home from the tube station after closing up the surgery for the night. The day had been an endless procession of patients with a variety of cold and flu symptoms. With a sigh of relief he let himself into 221B Baker Street, the only thought on his mind the cup of tea around which he would be wrapping his clammy hands very soon. But a loud crash coming from the upstairs flat brought his musings to a sudden halt.

"Sherlock?" he called out. Without waiting for a reply John bolted upstairs, his mind running disaster scenarios like a film: Sherlock battling an assassin, a science experiment gone horribly wrong, or possibly a psychotic client who had taken offense at the detective's candor in dismissing the 'boring' woes of the average mortal.

What John had not expected was to find Sherlock alone, standing in the middle of the room still wearing his coat, with the shards of his prized skull that used to occupy a place of honor on the mantlepiece strewn at his feet.

"Sherlock!" Watson's second utterance of the name had a completely different tone than the first, panicky exclamation. It now combined surprise, anger and exasperation. But when Holmes turned around to his friend there was a look in his eyes John had never seen before. Something so raw and hurt that he immediately regretted his harsh tone. But he also knew Sherlock's aversion to sentimental outbursts, so John bit back any concerned questions, especially the often asininely used 'are you alright'.

"Redecorating?" he quipped instead, only showing his concern and support by stepping next to Holmes. There was no reply from the detective, but John noticed the infinitesimal relaxation in the shoulders, and the usual shuttered, aloof look coming back into his eyes. "I'm rather surprised to see this one go, though. I remember, the first time I came to the flat you told me this was the skull of a friend."

"If you really remembered," Sherlock finally said, and only John's trained ear was able to detect the tiniest tremor in his voice, "you would recall that my exact words were a friend - of sorts."

"I stand corrected." John bent down and picked up one of the scattered pieces. "So what has this poor bloke done post mortem to be stripped of this status?"

Sherlock had turned away to stand by the window, gazing out into the dusk. "It turns out this skull does not belong to the person I thought." His fingers gave a nervous twitch. "Or rather, had been lead to think."

"So are you going to enlighten me, or do I have to ask Mycroft?" John couldn't suppress a small spark of glee when his question made Sherlock turn around, one eyebrow cocked in surprise.

"How..."

"Oh for heaven's sake, give me some credit. You were obviously out since you're still wearing your coat, and you don't make it a habit of visiting clients, they come to you. In addition, you said you were tricked and I doubt there is another person on this planet apart from your brother who can pull the wool over your eyes."

"My brother..." Sherlock muttered, turning back to the window. "There's the rub, isn't it? In fact, I had assumed that this skull belonged to my older brother."

Now it was John's turn to raise his eyebrows in surprise. "Your older brother - surely you didn't think that Mycroft was an imposter all these years?"

"Of course not." Sherlock turned away from the window and began pacing back and forth across the rug, a shard of the skull occasionally crunching under his footsteps. "I'm talking about my older brother, not the oldest."

"So there's a third Holmes brother. And you never mentioned him because..."

"Because I assumed he was dead, obviously. Turns out he wasn't. Isn't." Sherlock stopped right in front of Watson, that haunted, betrayed look once again in his eyes. "And I just found out that Mycroft knew all along."