She was recruited at sixteen: bright and cynical and able to tiptoe through secure systems with as little thought as most people gave to their hair. She never went to university, but has been quietly considering giving it a shot someday, just to see what it's like. She spoke three languages at twenty, and has picked up three more since. She can disarm most simple explosive devices. She can disarm and disable men twice her size in seconds. She can perform any dance that requires a partner. She can beat Sherlock Holmes at chess most days, but chooses not to lest he throw another of his epic temper tantrums. She can walk steadily and quickly in heels up to five inches. She can near-perfectly forge the signatures of twelve major political figures and seventeen minor ones. She can drive anything with wheels when required to do so. She can set broken bones and inject insulin and adjust dislocated joints.
She cannot change a diaper, cook anything that could be considered edible, or tell the difference between most colors. She is allergic to bee stings, pet dander, and strawberries. She is a lesbian, although she doesn't date and hasn't since her seventeenth birthday, when her girlfriend walked in on a midnight meeting with three unnamed members of MI6 and was promptly offered a lucrative research opportunity in Reykjavik. She is a vegetarian, and has been since she was seven. She tends to wear men's cologne, which contrasts nicely with most of her personas' ultra-feminine attire. She had pet turtles as a child, but her schedule doesn't allow time for pets and so now she has three small bamboo plants she almost always remembers to care for.
She appreciates Mycroft's genius, but doesn't bother to listen when he talks. The little dance they've been doing for years, where Mycroft gets to crow and explain and puff himself up, well, it's worth that small annoyance for the rest of the job. She's using the name Helena this month, but it's not working for her. She might give it up early — what's the point of spending twenty hours a day fetch-and-carrying for the puppetmaster if you can't take advantage of the perks? The clothing allowance, the salary, the travel, the tech…oh, and the ability to reinvent yourself whenever you get bored. This month's version, in khaki and red lips, itches and bothers, and she's never wanted to drop a persona so much, so quickly.
That evening, she happily returns to her default: Anthea, black skirt suits and too much eye makeup. She's rather proud of her eyes, as well she should be, and of her legs. Helena's khakis did nothing for her figure, exquisite tailoring be damned. The khaki and the white and the other things Helena used go in a black case, which she'll drop off at Mycroft's to be disposed of. She sleeps, and doesn't dream, because she's only got four hours to sleep before she has to be up and dressed and prod South Korea into reconsidering those executions. And Mycroft will want his usual order from the bakery on Downing Street, and she'll have to control the sugar content so that his diet's not wrecked, and she'll have to break the wrist of the bodyguard she's realized is a plant, and it's a busy day overall, so dreams have no place in her scant sleep.
The next day, she's almost happy to get to be Anthea again for a while. Mycroft has learned to track her name changes at last, and greets her correctly, and she accomplishes everything on her three-hundred-and-twelve item to-do list, including ordering John Watson a winter coat from Mycroft's preferred clothier and purchasing symphony tickets for Mycroft's mother's birthday. She'd prefer if he'd hire another assistant for these tasks, but he never will, because Anthea doesn't need to be reminded of anything, ever, and yet allows him to act like she does. He gets to play boss and she gets…well, everything.
She rather likes John Watson, with his crooked smile and limp and utter disinterest in betraying Mycroft's brother. Mycroft had almost nothing but praise for her, and she knew it. Sherlock loathed her no more than he loathed anyone else, and had learned not to attempt to intimidate her after he'd ended up on the floor, one arm twisted and creaking, his face pinned beneath her knee. He mostly ignored her now, which was how she preferred it. Mycroft's mother continues to think that Anthea is sleeping with one or both of the Holmes brothers, and Anthea no longer bothers to correct her. The woman has Alzheimer's, after all, and it's hardly worth the effort.
When Mycroft found Moriarty, Anthea — she'd stayed with the name for a bit, just until the crisis was over — had asked to be allowed to deal with him. Normally she had no desire to get her hands dirty when it was avoidable. Mycroft had decided to hand Moriarty over to DI Lestrade, and had bought Anthea a new Blackberry and a vacation in Monte Carlo as an apology. She so rarely asked for things, he hated to tell her no. Anthea came back tanned and richer and content: she'd had fantastic sex, tripled her money in the casino, and had managed to negotiate the release of three imprisoned artists in various countries. Mycroft, in the week she'd been gone, has gained two pounds and lost his cellphone, and had broken a toe stumbling around his home in the dark.
She sighs and brings him a no-sugar cupcake, and fixes the shoddy job his doctor had done of setting the toe, and makes a note to have the lights in his house outfitted with motion detectors. The cellphone is in the bottom drawer of his desk, like always, and Anthea solves two minor economic crises while Mycroft insists that the phone wasn't there yesterday.