It all started with a coat.
It was a very good coat. Sleek and dark with just a few too many pockets, and it was disappearing around a corner almost before Sherlock could take chase.
The Marquis had his own ideas about how things should work, and they very rarely involved being pursued through Colliers Wood (which, topside was rather mundane, and Below was something entirely different). There were, he was forced to admit when he was caught up to, situations where even the famed de Carabas couldn't always get his way.
But he could try.
Mycroft is to put it very mildly, rather cross. Because of course he knew about London Below. Some things are classified for a reason. And knowing about it had never spilled over into a desire to see it.. but he has a few useful contacts. When one is trying to run a country that just happens to overlap Somewhere Else.. and when that Somewhere has no regard for basic logic... It's useful to know a name or two.
In case of emergency, of course. And this certainly qualifies.
Sherlock is delighted by the whole chaotic, disastrous mess. The rules in London Below have a chemistry, a physics of their own, and he finds the madness very comfortable.
(The Marquis finds him disconcerting, and makes sure to keep an eye on him. Especially when he seems to come with friends.)
Molly and John are completely out of their depths, but they made fast friends with Richard over their shared floundering. Richard finds it reassuring to know there’s a soldier and a doctor around.
Besides, they don’t look at him oddly when he gets homesick for central heat and chain grocery stores.
Richard explains things in ways they understand, because he remembers how it felt to fall into London Below headlong and without a net. And sometimes he just has to shrug, because he's been here a year (he thinks. Is mostly sure. But time moves differently here) and some things still don't make sense to him.
Sometimes Lestrade is pinched with deja vu. But he’s never known anyone that lived on Baker Street. Funny that, he finds himself thinking-- it must remind him of somewhere near where he grew up. Odd things, human minds.
Eventually Mrs. Hudson finds a tenant for her upstairs flat, it's been empty for so long that she can't remember anyone living there before.
Nobody was surprised when Sherlock decided to stay, because London Below is where he belongs. It's strange and fascinating, and he's never going to be bored here because there's no time to be. Who needs drugs when he has to remember not to eat the spores from the Mushroom People, or wind up on the wrong side of the river?
This is an adventure. It's angels and great beasts, and bartering at the Floating Market for bits of things the world Above has forgotten.
Besides, he tells himself, it's not like anyone up there remembers him. His parents can't miss a son they don't remember having (and that stings sometimes, even though he knows it has more to do with magic than neglect).
But it’s a one-way trip. And he can’t ask the others to give up their whole lives for him. They have families, and other friends.. And even he isn’t that selfish.
This isn’t how Mycroft thought he would lose his brother.
Molly knows she has to go back. She has a life to get back to, and this is all very complicated but she doesn't belong in a place like this. London Below is a place for the brave, and she's never been that bold.
Then the Marquis is hurt, and of course she patches him up-- it's no trouble-- it's what she does-- and he doesn't know how to thank her because there are no doctors Below.
But there are a lot of people who need one. And Molly realizes that it's not her that needs them; it's London Below that needs her. Setting up a small practice turns out to be strangely easy.
As if it was waiting for her to arrive.
Rosie is waiting for John at home. And he's never been comfortable here, with its' strange rules and slanted morality. He misses his daughter, and his life.
He doesn't miss Sherlock once he steps through the wall. In fact, he doesn't remember ever meeting him at all. Some things are just easier that way.
But Mycroft reaches the red brick and stops.
He needs to go. His life is waiting for him on the other side of the wall and he's already so very late.
When he turns and walks back, Sherlock holds onto his arm and digs his fingers into the fabric of his jacket like he could keep him there. Mycroft doesn't have the words to explain that his place is with his brother.
Wherever that may be.
He expects to regret his decision to stay. But he doesn't.
The Marquis is only a little envious. His own brother drives him six flavours of mad, but he hasn't seen the Holmes boys fight. Yet.
None of them are getting any older, and sometimes they catch glimpses of the world Above through the grates.
The world doesn’t look back at them.