"Hmm..." Arkadia stood in front of the flat, wondering what mysteries it held.

A cheerful, elderly woman came out. "Greetings, dear!"
She said with open arms.

Arkadia smiled politely, but the lady brushed past her and hugged Mycroft. "I always love when you visit!
Now wait, I have to give the poor something to eat" Shee looked at Arcadia.

Mycroft looked fearful for Mrs. Hudson, and immediately cleared up the confusion when he saw Arkadia's dangerous smile.

"Oh, Mrs. Hudson, this is Lady Arcadia Markus. I have called her as my guest for a recent case. I talked to you about my brother's new roommate?"

"I'm sorry, dear" Mrs. Hudson apologized nonchalantly.

"It's nothing, I guess my disguise worked" She said triumphantly and clapped.

"I have a feeling you and him will get along great" Mrs. Hudson said. "Come along, dear. I've made tea"

"I believe I should take my leave now" Mycroft said, and stalked back into his car.

"Ah, here we are!" The door opened to the most dustiest, yet organized room ever. A tinge of nicotine stained the air, a smell of rotting corpses came from the kitchen, and a big yellow smiley face was painted on the wall with bullet holes. Arkadia loved it.

"I'll leave you to tour the place"

"How much is the rent for this place?"

"I only ask for a hundred pounds, but seeing you, I'll settle for fifty"
  "Two hundred it is, then" Arcadia decided sharply.

She ran and flipped into the musty air off her feet and tucking in mid air, the coffee table barely missing her head, and landed on the couch on her feet. She dropped down and started napping.

  "Sherlock is going to give you an earful" Mrs. Hudson muttered, and left.

Timeskip

"Female, maybe... In her thirties...someone of my homeless network.. very athletic... take a look at her muscles..." A deep deducting voice judged.

Arcadia shot up and found two men staring at her. One was short, a little older perhaps, he wore a green jacket and casual jeans, and had short grey-blond hair.

"May I ask who are you and what are you doing here?"

The younger one was tall and slender, with high and sharp cheekbones, brown, curly hair, and unloving pale blue eyes that were trying pierce through her, he wore a black dress shirt and matching slacks with a black coat over it. If she could ever feel attraction towards someone, it probably would've been him.

"You must be Cherlock Holmes" She identified. And you must be John Watson" She pointed at John. She turned back to Sherlock. "Your brother called me to London last night, and he said I'll be staying with you, roomie" she grinned savagely and held out a hand. Sherlock grimaced.

"It's Sherlock" he stiffly said. "And I am not taking in any-

"Oh, calm down, I'll buy my own food, I'm on the couch, I'm incapable of charming your boyfriend away from you and it's not like I'm choosing to be here" So he lied to me... Arcadia realized.

  "Great. Best you'll stay out of our way, then" Sherlock said, and went to leave. Arcadia easily grabbed his arm and pulled him back in front of her.

"I can help"

"Do you have any experience in the field?" Sherlock asked, rubbing a hand over the place she pulled his arm.

"No, I'm an consultant assassin. Mickey told me you guys have some dude called Moriarty to handle; and I'm still confused by what he meant. Usually, handle means hack one to pieces and use them as a handle but it could also mean handle before throwing them off a cliff"

"Mickey?" Sherlock asked. Assassin, explains her physique.. He deducted.

  "Mycroft" John corrected. 

Sherlock's frozen blue eyes stared into her. Too bad there was so much inside of her that wouldn't be displayed on her body, that one would have to personally know her to see through her.

Nevertheless, Sherlock smiled. "Let's eat supper, shall we? Can't think on an empty stomach"

John gave him a funny look. Apparently he didn't smile very often, Arcadia deducted, but shrugged it away. Arcadia stood up and followed the soldier and the detective in the hat out.

They didn't have to go anywhere at all. Speedy's was a sandwich bar and a local hub for most residents at Baker Street.

Sherlock slid into a seat and offered Arcadia one beside him.
  "Thanks, I didn't expect that from someone like you" Arcadia commented.

"The most entertaining occurrences are the unexpected ones" Sherlock corrected. "What are you ordering?"

Her voice quickly turned serious. It was scary how they both believed she was going to be friendly. "Some fries and an explanation for why the fuck you called me here"

"There are no fries here, but I will enlighten you on that very delicate subject," Sherlock sat up. "Your very distasteful septum ring has an engraving on it, something used on slaves in ancient times and guessing by Lady Markus's barbaric tastes I've heard of it's very possible to be the same case here, but your thickskulled facade says otherwise, so either Arkadia Markus is decomposing in a trunk or you, are a spy from our friend Moriarty" He finished.

"How about you just quit your smartass crap and tell me why I was called here?" She snapped. "And as for my proof, you won't believe me anyways and even if I'm not, I still need to know why the hell your brother called me here. If I was a spy, wouldn't I be seducing you like that Adler hoe? You seem to not need me, but I doubt you'll live long" She stood up.

"And why is that?" John asked.

"I don't know this Moriarty dick, but by how big you make him to be, I wouldn't be surprised if you die in the next ten seconds. Such  mind like yourselves are attracted to your equals or above just as easily as you pretend to be repelled by them." She stormed out of the diner, offended to have been interrogated like that.