Ok, a bit of background for this story. It's after the whole Derek / Addison thing, and Meredith and He are FINALLY together, however Addison is still working at Seattle Grace. Some bits from all seasons (I'm half way through season 5) and not all coherent or in order. So don't shoot me. Just enjoy . And yes, I am aware I have another fic on the go – "Family ties" (check it out) and it's not complete. Ok, on with the story. Thanks.

In the small, square MRI review room, Meredith and Derek sat talking, waiting for Mrs Brightmen's scan to load onto the screen. Meredith's mousey brown hair was tied up in pony tail a little above the nape of her neck, and a curled lock hung in front of her face, tickling her rosy cheeks. She was sat with her back to the MRI screen, on the counter top, feet resting on Derek's thighs. He gently tied the laces of his girlfriends worn blue converse sneakers. He grinned up at her. "Still on for dinner tonight then?" He asked, reminding her of his booking at 'Bella Spaghetti', his favourite Italian restaurant.

"Of course" Meredith smiled, she'd promised she'd go, Izzie had even helped her pick out a nice outfit to wear. She'd rather eat cold Chinese take out food, but Derek wanted to do something special to celebrate them over coming all that they had. His wife had shown up, and tested the Grey-Shepherd relationship to no end, they had split up, gotten back together, dated, had space, and finally they were back on track.

"Good" he grinned, and rubbed the back of his hand against his two day old stubble. "And maybe after we can go back to your place…" leaning forward he kissed he neck, just below the jaw line "and have desert…" he kissed her again "And so on," and again, "and so on…"

Meredith smiled and enjoyed the kissing. "Maybe" she replied. "But I'm on Addison's service tomorrow, so I will need at least a little sleep" she twirled one of Derek's black curls around her finger and tugged playfully.

"I'm sure I can talk around if she starts picking on you…" Derek teased. Meredith laughed, "Scans are in." He announced and they turned to inspect the screens. Together they looked closely at the scans and both made sad and sympathetic noises at the screen.

"That's funny, those noises sound just like the ones I heard mom saying to Addi when she found out you had a girlfriend." Came a voice from the door.

Meredith and Derek span round from where they were looking to see a teenager leaning against the door, wearing black leggings, a checked shirt, donned with jewellery, a cardigan and bright, red, familiar looking hair parted on the side, and clipped out of her face. She folded her arms and put her weight on one hip. "So this is the slutty intern you left Addison for."

"Uh, excuse me!" Meredith said, offended.

"Ally…" Derek began.

Meredith looked at Derek unable to read his face. "You know her?"

"You're not allowed back here." He told the girl, standing up, and putting his hands on his hips.

"Like that ever stopped me in New York". She said stepping further in the room.

"This isn't New York, Ally."

"I know. It's Seattle – sure does rain here a lot!" She looked at the scans on the screen behind them, "I take it those big black splodges aren't good eh?" She asked pulling a face.

"I'm sorry, who are you?" Meredith asked, moving so she blocked the girls view of the confidential pictures.

"Meredith," Derek said gripping her hand. "Page Dr Montgomery. Now."

"And say what?" She asked pulling her specially decorated 'sparkle pager' which gave her the power to steal any surgery from the other interns she wanted. She had the power!

"Tell her that her little sister's here." Derek said finally, as he shook his head.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

"Meredith Grey, this is Alyssa Montgomery, Addison's younger sister." Derek introduced, still surprised at his ex-sister-in-law's sudden and unexpected appearance.

"Does Addi know you're here?"

"Well know your girlfriend has paged her, I guess she does." Alyssa replied, shifting her heavy bag onto another shoulder.

"Are you here on vacation?" Derek asked, leaning against the wall.

"Not so much…Mom and dad sent me to live with Archer in L.A for a while." She paused and giggled. "That didn't work out so well. So I told them all that I'd spoken to Addi and she'd agreed to have me over summer."

"…But Addi doesn't know?" Derek asked, understanding the way this 'troubled-teen' worked.

"Got it in one" She smiled a sort of angelic smile. "So," She turned to Meredith, "What's the nightlife like round here?"

Addison appeared in the doorway behind her, white coat glistening, hair dancing around her face "Alyssa Katherine Louise Montgomery." Meredith watched as Alyssa's face paled for a moment.

She turned round to look at her sister. "Hey sis, you look good!"

"You look like you're in major trouble!" Addison retorted, hands on hips, eyes pouring down on her younger sister.

"So what else is new?" Derek muttered sitting back down besides Meredith while placing his hand on her back. Meredith bit her bottom lip to stop herself laughing. She'd never seen Derek like this before.

Addison rolled her eyes. "Come on Ally, lets go talk." She sounded resigned but a little happy to see her sister.

Ally repositioned her bag, and went to Addison's side, where they both put their arms around each other's shoulders and shared a quick squeeze. "See you later Derek. And, sorry about the slutty intern comment Marigold…"

"It's Meredith," Meredith, Derek and even Addison corrected. The three doctors exchanged a look of surprise and quickly covered their looks with polite smiles.

"Whatever." Ally said, smiling. She caught Meredith's eye and gave another, quick, secret smile, which Meredith understood.

After the Montgomery sister's left their presence Meredith sat on the chair. "Wow." She said.

"I know…"

"That was…"

"Awkward…" Derek finished.

"Is she was Addison was like when she was what? Eighteen? Nineteen?" Meredith asked, shocked at the sister's similarities despite their obvious age difference.

Derek laughed. "The opposite. Addi was a good girl, never stayed out past curfew, always top of her classes, never drank until she turned 21, never crashed her car or got points on her license for speeding. And of course, she always had perfect boyfriends." He grinned, meaning himself.

Meredith elbowed him, but smiled, "Why doesn't it surprise me that Addison Montgomery was perfect?"

Derek smiled. "Her parents were hard though. Upper class, aristocrats, they had Addison and Archer's lives planned out for them in the womb. The finest education for all of them, music lessons, horse riding, sports, clubs… they were pushed, and both of them succeeded to be honest…"

"And Alyssa? She's a lot younger than Addison and Archer." Meredith asked, hitting the print button on the screens.

"Ah. She wasn't planned, an accident. And was never allowed to forget it. Though she did play up to it." Derek said going to the printer and taking the films out for a closer look.

"What do you mean?" Meredith asked.

"She rebelled. She's been in, I think four private school, and a bording school which all threw her out. When her parents tried to get her horse riding, she rode the horses miles away, got off, and let them go – then hitch-hiked back to the house. She was I think 6, the first time she did that. For her 16th birthday, she got a brand new Porshe Car. Crashed it about 20 minutes after getting in, it was totally written off, and she broke her arm. Did the parent's car about the arm? Nope." Derek sighed. "She's not stupid, she's really smart, but it's like she's determined to do the opposite of what her parents want."

"No wonder" Meredith commented. "With parent's like that, I'd want to rebel too!" he sighed again, "You like her, don't you?"

He nodded. "We got on really well actually. Had a few things in common, same taste in music, the outdoors…we talked you know, more so than she did to her own brother I guess. And she'd listen to me…if she'd been in trouble…sorry, when she'd get in trouble with her parents, she'd come to me and Addison, Addi got irritated, but I like to think I helped…"

Meredith smiled, "Her knight in shining armour hey? What is it with you saving dark and twisty girls with family issues?" She kissed him softly on the lips, and linked hands with him.

He laughed and squeezed her hands. "Lets go tell Mrs Brightmen the bad news, shall we?"

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

"Ally I swear to god, you cant just get on a plane and fly out here without telling anybody!" Addison said sitting down around a table in the Attending's lounge, she passed her sister a mocha from the coffee machine, and poured herself a black coffee.

"Archer knew I was coming." Alyssa retorted, taking a sip from the cup and burning her tongue.

"If he did, how come he never told me?" Addison asked, blowing on the drink first before taking a sip.

"Because I told him mom had told you to have me this summer." She explained.

"Why did you do that?"

"To surprise you" Alyssa grinned, leaning back in the chair.

"You know I hate surprises."

"Exactly."

Addison took a sip of her coffee again and looked into her sister's green eyes. "So what happened in L.A that was so awful you had to come here?"

"Could I not just have come to see my favourite big sister?" She asked innocently, eyes glistening.

"Ally, don't use those eyes on me. I invented those eyes!" Addison told her, smiling.

"Archer and I fell out." She explained, chewing the inside of her chin.

"What did you do this time?" Addison asked her sister exasperated.

"Why do you assume it's something I've done?" Alyssa asked, offended. Addison raised her eyebrows. "Ok, so normally it is my fault…this time wasn't."

"Right…"

"Addi! It wasn't."

"I've heard that before! Hang on, how did you pay for your flights?" Addison asked quickly swapping the subject. "I thought dad limited your account after the New York disaster."

"He did. Archer left his card lying around." Alyssa giggled "I decided it was a nice goodbye gift he could give me."

"Ally! You are in so much trouble when he finds out, let alone when mom and dad do."

"Please don't tell them!" Alyssa begged. "I didn't tell anyone about you and Mark."

"Mmm, look how that one turned out."

"That's your own fault for being stupid and sleeping with his best friend, in your own house. If you didn't want to get caught, you would have been better at hiding it, seriously Addi, it's not brain surgery…or gynaecology" She smiled at her little in joke.

"If it's so easy not to be caught if you don't want to be caught, why do you always get caught?" Addison retorted. Alyssa looked at her sister straight in the eyes, then it dawned on her, "Unless, you…want to be caught…" Alyssa looked down. "Why do you want to be caught? You just get in trouble!"

"Exactly." Alyssa said, helping herself to a bit of lettuce out of her sister's Tupperware box of salad.

"I don't understand…"

"How else do you expect me to get dad to notice me?" Alyssa asked shrugging. "My two older siblings are both doctors, a neurologist and a gyaenocologist, pretty dam high in their fields of expertise. Both incredibly intelligent, great lives, always were well behaved and perfect…well You more than Archer… good at everything… went to the best schools, got the best grades, got the best reputations. Boosted mom and dad's social standing having two incredibly intelligent and successful kids…and then the condom breaks…"

"Alyssa!" Addison reproaches her sister, and pulls a horrified face at Alyssa's crude analysis of her conception.

Alyssa ignores her sister. "The condom breaks and boom, nine months later pops out little 'Accidental Ally'" she finishes, her face falling as she recalls her childhood nickname, invented by her brother Archer. "Conceived down the back alley," She continued, remembering the nickname the snobby daughter of a snobby family that hated the Montgomery's.

Addison laughed. "where the hell did you get that from?"

"It's not funny. And Archer started calling me Accidental Ally when I was like four, and Jessamina Tory added the other bit when we were in Middleton Private together."

"Nice girl." Addison said shaking her head.

"So, I heard Mark came all the way out here to win you back." Alyssa asked.

"Where'd you hear that?"

"Mark told me he was coming all the way out here to win you back."

"Oh yeah? What else did he tell you?" Addison asked, making a mental note to grill Mark, who had, on many occasions shared knowledge with Ally, that he certainly should not have done. Alyssa shrugged. "So kiddo…where's the rest of your stuff?"

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Mark Sloan stood with a group of doctors and nurses, stressing the importance of the care that was needed for a particular patient who had had a cancerous tumour removed from his face, which had caused tremendous damage to an artery, and therefore the poor patient was very delicate and attention and caution had to be rigorously activated.

"If any of you so much smell a bleed, get in there and stop it! Then page me." He looked around his colleagues who all looked slightly scared, and took pride in the fear he instilled in them.

Amongst the group of white robed Seattle Grace employees stood Drs Meredith Grey, her sister Lexie Grey, Alex Karev, Izzie Stevens, George O'Malley, Christina Yang and a number of other interns.

"Now," He continued "I'm going to need one of you pathetic excuses for doctors to scrub in on his next operation." As he spoke, everyone raised their hands, but none as eagerly as young Lexie Grey, who had, as always, positioned herself right in the centre front. Mark grinned on the inside, revelling in his power. "But you need to answer a question first." All hands went down, waiting for the question. "How, exactly do I like my caffine?"

Alex Karev was the first to answer. "Coffee."

"Wrong"

"Cappuccino!" Yang shouted out.

"Nope"

"Latte?" Meredith tried.

"Couldn't be more wrong Grey."

"Mocha?" Lexie tried.

Mark looked at her. "I'm surprised at you little Grey. Wrong. Come on, can't anyone of you answer this simple question???"

"Cappuccino, steaming hot, no cream, two lumps of sugar, brown, not white." Alyssa said, walking away from Addison, who was signing charts off at the nurses station, opposite to where the doctors where huddled. The group looked around, surprised to see the teenager, and confused as to how she knew the answer. "Stirred clockwise" She finished, smiling. "Hey Mark!"

"Ally?" Mark questioned, beaming. Alyssa, wasting no more time ran through the now parted crowd and into his open muscley arms. He lifted her, and squeezed her tight, spinning her round. She landed on the floor and hugged him again. "What the hell are you doing here? Or should I say what did you do now?" They both laughed. Then he took her hand, lifted it and made her spin beneath it. "You've grown" he announced.

"No I haven't" she laughed, "You've shrunk." Mark laughed too, then ruffled her hair, much to her displeasure. "Mark!" She moaned. "So," she started, whilst she fixed her now messed up hair "I hear your sleeping with my sisters ex husbands new girlfriends half sister…or something… isn't that like … incest?" Immediately, everyone stood behind her started gossiping, and talking. Alyssa turned round, as if noticing the others for the first time.

"Ally." Dr Montgomery called.

The doctors all looked between the new stranger and Dr Montgomery. Meredith whispered to her friends "Sisters." Which, of course, was overheard by everyone, and caused a new level of gossiping to ensue.

"What's she doing here?" Mark asked Addison, putting his arm round his young friend.

"I'm staying her for a while!" Alyssa announced, grinning.

"Sweet!" Mark replied, high fiving her.

"Only until I can convince dad to take her home" Addison muttered, trying to be discreet, which of course was, in Seattle Grace, impossible.

"Oh what you do this time?" Mark asked, obviously finding it funny.

Addison took her little sister's hand and tugged her closer, and away from Mark. "Mark Sloan, do not encourage her. Come on Ally…".

Alyssa reached up and kissed Mark on the cheek then ran after her sister. The interns and residents watched the Montgomery sisters walk away, their red, straight hair, swaying in identical fashions.

"Are you tying to get me in trouble?" Addison asked as they walked towards the entrance of the hospital.

"Not purposefully, but if it happens, I guess it's a bonus" Alyssa laughed, linking arms with her big sister. Addison smiled and bent to kiss her on the top of her head. "I've missed you Addi…"

"You too kiddo." Addison replied. "So are you going to tell me why dad sent you to Archer in the first place?"

"Where are you living now?" Alyssa asked, smoothly changing the subject.

"Ally…" Addison started.

"Ah Addi!" Came a familiar voice from behind them, "I need you to do some extra time for me, we've got a….I'm sorry, do I know you?" Richard Webber, chief of surgery asked Alyssa, slightly confused.

"No." Alyssa replied, smiling then turning around to leave.

Addison caught her hand and pulled her back besides her. "Richard, this is Alyssa, my younger sister, Ally, this is Dr Webber…Chief of surgery" She added through gritted teeth, stressing her need for respect.

"Ah chief. Good for you!" Alyssa winked at him.

"Ally!" Addison raised her voice and gripped her hand a little tighter. "Sorry chief, she's a teenager!" she tried to laugh it off. "She's staying with me for a while."

"Oh…well I hope to see you again." He smiled, and to Addison's surprise, she smiled back. "So I take it you can't work tonight?"

Addison looked at Alyssa then back at her boss "Erm…I guess…" She caught Ally's face drop, "No, I cant sir sorry…" The chief nodded and said he understood, then left muttering. "Up for Chinese food?"

"Definitely," Alyssa replied smiling again.

So that's it for now.

Please tell me what you think

Good / bad / indifferent

Should I continue?

I have a few ideas in mind. Let me know

THANKS : )