I do not own or have anything to do with these amazing characters.

Molly

There is a woman who lives in Sherlock's mind palace.

He can't remember when she appeared, peering in his rooms and darting between the shadows. She's not real and never has been. His first deduction of her, when he stumbled upon her going through his catalogue of hair samples, was that they had met and he had subsequently deleted her. The look she gave him at his flamboyant conclusion, suggested he had been wrong and he gave up when she started snickering into her hair.

He used to try to catch her when he was younger, chasing her through the labyrinth of corridors and stairwells. Everytime he got close to snaring her, she would spin around giggling before ducking into a room.

She disappeared during his drug years. They had a fight over his addiction, she slapped him before turning around and running into the darkness. She had called him a coward and she had cried. He hadn't felt anything, especially not remorse, with all the cocaine floating through his blood stream and let her go. That changed when during a particularly nasty low, she pulled him through the waking nightmare and back to safety. As soon as he surfaced he found himself clinging to her body, breathing her scent and holding on to her hair. He swallowed his pride and admitted to that he missed her.

He went to his brother the next day and asked for help.

He didn't have a name for her for the majority of his childhood. He had childishly ignored her and drowned her out with an intensive studying of the violin.

When he became a teenager, he used to tease her by calling her Moggy. It seemed fitting given the fluffy cardigans she opted to wear and the random cat videos she forced him to endure when his attention drifted off. She hadn't been pleased with him and when politely (and not so politely) asking him to stop had failed, retaliated by reshuffling his room index and showing him porn in his dreams. When Mycroft started commenting on the cold showers and stripped bedding, Sherlock admitted defeat and apologised. It wasn't unnoticed that the rooms returned to their rightful state and his dreams were blissfully uneventful from then on, even through his difficult adolescent years.

He jokingly called her Molly when the memory is recalled. The name has sort of stuck now.

Sherlock doesn't really remember when she first turned up. If he had bothered to look into it, he probably would have noticed the pattern of her appearance and the traumatic death of his innocence. Redbeard and their adventures are in a sealed room at the back of his mind palace, so he's never acknowledged the connection. Molly, with that sad look on her face that irritates him, reminds him that he clearly doesn't want to. She never brings up Redbeard or the pirate days and Sherlock is never sure if he is happy about it.

Molly does not age though. She is the single constant in his ever changing world. He supposes that he draws some form of comfort from that, but he would never reveal that to her. Though her occasional smirk has him believing she already knows.

He relies on her to protect the mind palace. To fight the intruders who threaten the peace and restore the rooms when he deletes them in a childish temper tantrum. Sometimes she does and many times she doesn't. She likes to reminds him that all actions have consequences and his usual response is to not talk to her for days as he rebuilds the room the old fashion way.

Molly has her moments too.

She doesn't speak to him through the whole The Woman incident. It takes him much longer than he likes to admit, to realise that the woman has intruded on Molly's turf and as soon as he discover the error he tries to delete the room. Molly doesn't let him and once during a moment of jealous sulking (a rare and thankfully brief occurrence) opened the room and let her loose in the mind palace.

The destruction was like a forest blaze and took a long time to repair.

Sherlock has never mention Molly to John.

He's never really been sure how to broach the subject. John accepts the mind palace and his other 'eccentricities', but to admit that there was a woman walking round his psyche like she owned the place would probably be one oddness too far. Sometimes he wishes he could, advice on how to handle one of Molly's moods would be beneficial. Though, with John's track record with women, he acknowledges that he may be better off with his own trial and error approach.

John occasionally asks him if he gets lonely, without a constant companion to walk with him through life. A wife, a husband... a lover. Sherlock never answers him and John surmises that he may be the only one to stay and watch over his friend.

Sherlock doesn't know how to tell him that he is never alone or lonely. That he has his companion for life. He wants to tell John all about the woman that looks over him and loves him. That walks beside him through it all.

Molly is his life and he would be lost without her.

The End.