"So what might we deduce about his heart?"

"I dunno"

Mycroft sat back in his seat, he then produced another manila coloured file and placed it on the table and sat back. He deliberated whether or not he should share this information, after all this was his story to share. He cleared his throat leaning forward slightly.

"What does the name 'Erin Lorgan' mean to you"

John stared blankly at the man in front of him, "Nothing, why."

"I didn't expect you to, Erin Logan was an acquaintance to Sherlock of sorts. She was the reason my dear brother started taking drugs 10 years ago"

Mycroft passed the file over to John who opened the cover and looked down in shock. In the file were many documents, medical and others, but what John found the most surprising was various pictures of a young Sherlock and a girl who looked to be around the same age with him. She had brown hair and pale skin, she looked fairly ordinary - someone who wouldn't stand out in a crowd. Sherlock having a friend in the past didn't entirely shock him, he was his friend now after all, what he didn't expect was Sherlock and this girl, presumably Erin, holding hands and laughing.

"What is this" John asked quietly unsure if Mycroft was playing some sort of trick.

"These are pictures of Erin Logan and Sherlock in 1999 and 2001, Sherlock was 20 at the time and she was 19." Mycroft stopped there, he knew he may be crossing some sort of boundary to inform John of Sherlock's and Erin's relationship. He knew that he couldn't tell John that this past Christmas Sherlock was upset over a death, just not Irene Adler's as John had assumed.

"Why are you showing me this?" John asked, he couldn't make sense of the situation at hand.

"My brother has become somewhat reliant on you . You are his closest friend at it is your responsibility to make sure that Sherlock doesn't relapse, to do this you need to know all the facts and triggers." Mycroft knew that it wasn't Johns responsibility, but Sherlock hadbecome dependant on John.

Before John could say anything Mycroft pulled one of the medical forms from the file and handed it over to John.

SURNAME : LORGAN

FORNAME : ERIN

D.O.B : 1980, NOVEMBER 13

D.O.D : 2001, DECEMBER 24

GENDER : FEMALE

MOTHER : JESSICA LORGAN nee GALLAGHER

FATHER : PAUL LORGAN

ADDRESS : 21 NORTHUMBERLAND STREET, LONDON

DOCTOR : DR. CHRISTOPHER COOPER

DIAGNOSES : TERMINAL CANCER, BRAIN TUMOUR

DIAGNOSED : 1992, SEPTEMBER 15

IN CASE OF EMERGENCY CALL : SHERLOCK HOLMES, 0792634257

"Oh my god, I had no idea Sherlock had any friends- I always thought of him as a bit of loner" John admitted guiltily.

"He was," Mycroft said, seemingly unbothered, "until, he met Erin. She was the first person besides mummy to actually accept him, they were very close. Which was why it was so hard for Sherlock afterwards. Terrible. That's why he started taking drugs. You are the first person since her to accept him, I think that's why he likes you so much. Though he'll never admit it mind you. He won't even admit to knowing her, she's probably locked away in his 'mind palace' now"

Now John thought about it, the other day when Sherlock was in his mind palace John swore he heard Sherlock mutter 'Erin' but dismissed it thinking it was for a case, when he told Mycroft this his face twisted into concern.

"If he is thinking about her again we need to keep an extra close eye on him" Mycroft sighed.

"Why" John asked confused and leaned forwards.

"Well its not my place to say. However, my brother is a very stubborn person so he won't tell you himself, and you need to know this."

Mycroft shifted into a comfortable position and ordered another cup of tea, as was the British way when storytelling. He sighed, hoping Sherlock wouldn't react too badly to John knowing this information.

December 1999, Hospital

Erin walked aimlessly through the corridors of , all of the hallways and rooms familiar after spending lots of time here since she was twelve years old. It was the last day of term for all of the med students, as a pass time she would watch the lessons through the door windows. When she was younger Erin had wanted to be a doctor, her plans had changed when they had diagnosed her with cancer. She had a brain tumour, they had been putting her through many ordeals of surgery and treatment 'trying to save such a young life', it had almost worked. Despite the fact that her brown hair had started to grow out and now reached her collar bone and she looked healthy, yesterday they had informed her that her cancer was terminal.

Now here she was, staring through the doors at the people her age laughing and exchanging gifts for Christmas, although she wasn't feeling too festive herself. Soon she would just be another cadaver on a slab, within about a year. She moved out of the way quickly just before the mass amounts of young adults swarmed out. She stood back and watched them quietly, she wished she could be like them not labelled as 'different', 'special' or whispered in hushed tones 'sick'. She was just like anyone else, just with some….limitations in how extreme she could act.

"See ya Mike" a blonde boy called as he walked backwards.

"You to, John, Merry Christmas," Mike called back. She had talked to Mike a few times and he had shown her his medical books. She envied him, he could be a doctor if he wanted, he had friends, he was normal.

The hallways cleared and Erin pushed herself of the white wall and began to walk the familiar route of bleached floors back to her plain hospital room. With her head down she didn't notice the young man walk into her.

What seemed like millions of papers went flying, Erin being her unsociable self tried desperately to catch as many of the stray papers as possible to prolong a start to conversation. As she bent down to grab a paper that was now settled by her feet, she noticed that the paper had information about a drug cartel. Great, its a police officer- that makes everything better, she thought.

Regardless of the boy she began reading it interested, before she could finish it was rudely yanked out of her hands. "Thank you, I do believe that was mine" the man said cruelly putting it on top of his file. "Sorry" she mumbled quietly, looking at her feet.

"Fine," the man said and continued walking down the hall. Most people would have went on about there day after this, not Erin. He hadn't shouted at her or given her a disapproving look, he just dismissed her. She watched the back of his head walk down the hall, his dark brown curls bobbing slightly.

So Erin, being Erin, chased after him.

A/N- hey this is the first Sherlock/OC fanfic that I have written, sorry if its a bit long. I quite like this idea so I'll update as much as I can. Like, follow and review please it makes me update.

DISCLAIMER: I only own Erin and any other OC's that might come up, everything else belongs to the BBC and ACD. As far as I'm aware I came up with the plot, if it looks familiar to you please just tell me and don't sue. :)