I accidentally Superlock.
The doorbell rings. It's late in the evening - odd hour for a client, and they're not expecting anyone. John glances at Sherlock just as two men barge into the flat.
"Nobody move, MI-5. I'm Agent Angus, he's Agent Young."
Imperiously, Sherlock unfolds himself from his chair and glares at them.
"Nice try, but no. Americans, and your accent is painful. Brothers, despite the obvious differences in facial structure. You're older, even though you're shorter, and you won't admit that it bothers you. You've spent most of your lives looking out for one another, living a somewhat transient, unstable life. Demon hunters?"
"What? How... what?"
"Your suits don't fit, you've nicked or rented them. You both smell of sulphur - not enough to be coming from you, but you've encountered it recently. Rough hands, you work with them and often expose them to harsh chemicals and rock salt. Your brother also has tell-tale bruises on his hand and at his neck, he's used a shotgun at an awkward angle in the past week or so. Defending yourselves on a regular basis, combined with the taint of brimstone - demon hunters."
The taller brother, silent until now, turns towards John, who has been watching the exchange intently.
"He's always like that. Sharp as a tack, and a painfully low tolerance for bullshit."
I may write the follow-up to this some day. I dunno.