This Chapter refers to the Events of S01E03. So dialogue and Story is took from that Episode and I placed Kate in it.
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Sherlock was still sitting in his armchair when Kate enters the living room in the morning.
"Morning." she says while taking John's laptop and sitting down in his armchair.
"What time is it?" He asks, looking at her straddled.
Kate checks the time on the laptop. "7 am."
"Where's John?"
"Here." John answers from the kitchen and enters the living room with a teacup.
"You know...I never got the chance to ask you how your first day at work was, John?" Kate asks and John starts to tell her how it went with excitement, till he leaves for another day at work.
Kate was just about to start to get ready when she has an idea and pops her head out of the tiny bathroom, looking for Sherlock.
"Can I be loud or do you need to concentrate?" she asks.
Sherlock frowns, confused why she even bothers to ask. "I'm waiting to leave for my flight to Russia anyways so...whatever."
"Russia?"
"Yes, it's for a possible case."
"Well then. Have fun I guess." Kate smiles and starts to get dress and put makeup on while dancing and singing to her favorite songs. When she turns around she jumps because she's surprised to find Sherlock standing in the door.
"Sorry, was I too loud?" she asks while stopping the music.
Sherlock shakes his head. "No, I was just wondering what this was all about? Fancy dress and makeup and also a good mood after what happened yesterday."
Kate rolls her eyes and leans over the sink to get closer to the mirror and puts her mascara on. "I have a date directly after work."
Sherlock stiffens. "A date? With my brother again?"
She starts to laugh and then applies her lipstick. "No, Sherlock. I went out with your brother once. He's way too old for me and I'm pretty sure he's gay, sorry to break it to you. I'm going out with a colleague."
"Gay? Makes sense somehow." Sherlock frowns.
"Yes. I mean first I thought he's just not 'capable of romantic feelings' like you but I think no one can completely isolate himself from feelings....I mean look at you, running around solving crimes with your best friend."
Before Sherlock can say more Kate gently pushes him out of the door and leaves for work.
Then date goes really well, her date Jim is a real sweetheart and Kate is sure that she will go out with him again.
When she returns from her date she already meets John, who also stayed out late with his current 'crush' Sarah, in front of the building.
"Hey John, had a good time?" She greets him.
"Yes! Do you think Sherlock's back already or...?" He asks while walking up the stairs but is interrupted by gunfire.
"Bloody hell!" Kate says storming up the stairs in worry.
John enters the living room first and shouts at Sherlock. "WHAT THE HELL ARE YOU DOING?"
"Bored." Sherlock signs.
"What?"
"I'M BORED!" he screams and pushes himself up from his armchair.
Kate just starts to laugh. "You're trouble, Sherlock Holmes." She walked towards the shelf in the kitchen and reveals two more guns. "And a very bad influence."
"Since when do we have so many guns in this house??" John asks shocked.
Kate shrugs and points them at the wall. "And that coming from the only person here that really learned how to deal with a gun...and has a license to actually buy them legally."
Sherlock snorts and Kate removes the safety from both guns.
"No!" John pleads, but she's already shooting at the wall and Sherlock joins her while John seeks cover.
"I.AM.BORED." Sherlock screams between every shoot.
"OK!" John says before stepping forward and taking the guns from your hands and taking the bullets out.
"I get why you do it. It's fun and no one's hurt." Kate laughs at Sherlock while sitting down in John's armchair.
"What's up with the criminals?!" Sherlock sighs and lets himself fall backward on the sofa.
"What's with that Russian case you texted me about?" John asks while putting the guns away.
"Yes, have you ever been to Russia since you're back already?" Kate frowns.
"Yes. Not worth my time." Sherlock answers with a bored voice.
"Shame." John says sarcastically and enters the kitchen.
He stops in front of the table with all the experiments. "Do we have anything here? I'm starving."
Kate ha a hard time hiding her laugh when John approaches the fridge.
He opens it and immediately closes it again. "Oh fuck." He holds on to the fridge but seems a bit week on his legs.
Finally the laugh breaks out of Kate and Sherlock looks at her, also slightly laughing.
John opens and closes the fridge again. "It's a head."
"Good deduction Mr. Watson! No wonder Sherlock takes you on cases with him." Kate laughs.
"What so funny about that? There is a head in the fridge!" John panics.
"Just tea for me thanks." Sherlock says in an amused voice and Kate laughs even more.
"A bloody head!" John nearly screams with a higher voice than usual.
"Yes, where else was I suppose to put it??" Sherlock asks seriously.
Kate is laughing tears by now while Sherlock explains his experiment to John.
"Calm down John, I was the one who did the investigation on his body, when his head was still on his head. As far as I remember he was a rapist or some shit so...who gives a shit?" Kate tries to calm him.
"By the way, I finally checked your blog." Sherlock changed the subject.
"And?" John asks still a bit shocked while sitting down in Sherlock's armchair.
"'A study in pink'? Really?"
"I liked the name." Kate mentions.
"But nobody cares about your opinion since you weren't in it." Sherlock snaps back.
"There was a lot of pink. Did you like it?" John asks curiously.
"Ehm...no."
John frowns. "I thought you'd be flattered?"
"Flattered? 'Sherlock sees through everyone and everything in seconds but what's incredible tho is how spectacularly ignorant he is about some things.'"
Kate rolled her eyes. "Yeah about that..." She tried to step in.
"No hang on!" John tries to justify himself.
"What? Did you mean it in a nice way?" Sherlock asks sarcastically. "I don't care who's prime minister, who's sleeping with who..."
"Or that the earth goes around the sun." Kate mutters under her breath and then looks up at Sherlock with a raised eyebrow.
"Oh not that again! Of cause John told you." Sherlock groans.
"Nice one!" John laughs and high fives Kate.
"It's not important!" Sherlock shouts at them.
"Not important?!" John asks.
"It's primary school stuff, how can you not know this?" Kate laughs.
"If I ever did I deleted it."
Now it was Kate's turn to frown. "Deleted it?"
"Listen, this is my hard drive." he says pointing at his head. "And it only makes sense to put things in there that are useful. Really useful! You all put any kind of rubbish in your heads and that makes it hard to see the things that matter!"
"I kinda get it but still..." Kate admins. "That trash we put in our heads is what makes us us and what makes us to individuals. For example, knowing every character from our favorite TV show or the lyrics of our favorite song. That's what humans do. We decide ourselves what we find to be important. Even you do, you can play violin and know the notes so isn't that also trash in your head? Cause what do you need that for to solve crime or whatever it is you do?"
Sherlock holds her look for a few seconds before John breaks their bubble.
"But it's the solar system?!" John shouts still not convinced.
Sherlock groans. "It doesn't matter! All that matters is work and without that my brain rots. Put that in your blog or better stop giving your opinion about anything out in the world." Sherlock snaps and turns around, so his back is facing them.
"Sherlock!" Kate growls.
John gets up without another word.
"Where are you going?" Kate asks him.
He grabs his jacket. "Going out."
Sherlock turned around to watch him leave and gets up to watch him walk away through the window while Mrs. Hudson comes in.
"Hello, Martha." Kate warmly greets her.
"Hello, dearie. I went to the store and got you some things." She says, placing her back on the kitchen table. "Did they have a fight again?"
Kate nods and looks at Sherlock. "Don't worry. I bet there will be another murderer or something soon."
"Yes, that will cheer you up hopefully." Mrs. Hudson adds before she leaves again.
"Hopefully." Sherlock signs.
Before Kate can say anything else there is a loud bang and in the next moment she finds herself flying through the living room.
When she first opens her eyes she closes them immediately again to stop her head from spinning. After a few deep breaths she manages to open them again and finds herself clinging on the kitchen table on which she is half laying. There is fog everywhere and she has a hard time breathing. Kate tries to lift herself in a standing position but stops directly when she notices that the shards from Sherlock's experiment vessels are all over the table and under her hands.
"Fuck. Sherlock?" she finally brings out but only get a groan as an answer before she starts to feel dizzy again. The last thing she hears is sirens outside and someone running up the stairs and calling out Sherlock's name, who sounds like Mycroft.
Kate wakes up with a groan in a lying position and as soon as she's able to take her surrounding in she notices that she's laying on the sofa and that Mycroft and Sherlock sitting in the armchairs watching her.
"Good to have you back Kate." Mycroft says with his fake smile.
Kate sits up and holds her head. "Bloody hell."
Mrs. Hudson rushes to her with a glass of water. "Slow down darling. You took quite the hit." Kate drinks it in one go and Mrs. Hudson pets her cheek. "I'm gonna get you some more water."
Mrs. Hudson leaves and Kate groans again. "My head and ribs hurt like hell."
"The doctors checked you as good as there could. You were only half awake. I don't think you remember any of it but since we live together with a doctor we could convince them to not take you with them. As it seems you had luck. The cuts in your hands and torso aren't too deep." Sherlock says and Kate notices that both her hands and her torso are wrapped up. "And the liquids of my experiments weren't harmful to the skin or anything so...besides bruises and a concussion you're good."
"Are you okay?" Kate looks up to him.
"Yeah, I'm fine. A few scratches but nothing big. I wasn't directly in front of the window like you."
"What the hell even happened?"
Before Sherlock can explain you hear John storming up the stairs calling both your names. Once he entered the living room he made a relieved sound to see you both alive and breathing.
"John." Sherlock says while playing a tune on his violin.
John tried to catch his breath from running up the stairs. "I saw it on the telly, are you both okay?"
"Oh yeah, I'm fine. You need to check Kate again tho. Gas leak apparently."
"I can't." Sherlock says turning back to Mycroft.
"Can't?" Mycroft asks, clearly not believing him.
"I can't spare the time."Kate raises an eyebrow and crosses her arms while sharing looks with John.
"This is of national importance." Mycroft points out.
"How's the diet?" Sherlock asks bluntly to change the subject.
"Fine!" Mycroft answers annoyed and Kate snorts.
"Maybe you can help me get through to him Kate? John?"
"What?" John asks, still catching his breath from running.
"I'm afraid my brother can be very intransigent."
"If you're so keen why haven't you investigated?"
"No, no, no. I can't possibly be away from the office any length of time. Not with the Korean election so..." everyone looked at Mycroft in confusion. "Well, you don't need to know about that, do you? Besides, a case like this requires leg work." He says with a disgusted expression and Sherlock's head shoots up just as he made another tone with his violin.
"And John how was the lilo?" Sherlock tries to change the subject again.
"Sofa Sherlock, it was the sofa." Mycroft and Kate say at the same time.
Sherlock gave John another look. "Oh yes, of cause."
"How??...Never mind." John states.
"Sherlock's business seems to be booming since you and him and now Kate became....pals..?" Mycroft says in attempt to bring the previous topic back on.
He also looks at Kate now. "How is he to live with? Hellish I imagine."
"We're never bored." John answers and Kate nods very enthusiastically.
"Good. That's good, isn't it?" Mycroft says with his usual fake grin and Kate shrugs unsure.
Mycroft gets up and wants to hand Sherlock the documents for the case he wants Sherlock to solve but Sherlock just stares at him instead of taking them, so Mycroft makes his way to John and Kate who sit together on the sofa now. He hands each of them a pile of paper and starts to explain the case of Andrew West, who was found dead on the train treks with his head smashed in this morning.
"Jumped in front of a train?" John asks.
"That seems to be the logical assumption."
"But?" Kate asks while looking through the files.
"But?"
"You wouldn't be here if it was just an accident?"
Sherlock laughs and Kate looks at him for a second before looking back at Mycroft, who starts to explain that Mr. West was part of a program and took care of an important memory stick that is now missing.
"That wasn't very clever." Kate marks out and sees Sherlock smirking again.
"It wasn't the only copy. But it is secret, and missing."
"Top secret?" John asks again now.
"Very. We can't risk it falling in the wrong hands." He turns around to Sherlock again. "You gotta find those plans, Sherlock. Don't make me order you."
"I'd like to see you try."
Kate snorts at that and Mycroft gives her an unhappy look.
"Think it over." He says to Sherlock again before turning to John and Kate to shake their hands. "Goodbye, John. Kate. See you very soon."
Sherlock starts to play nervous music with his violin while Mycroft leaves and John and Kate just give him a strange look till Kate bursts out in laughter.
As soon as John knows that Mycroft can't hear them anymore he turns to Sherlock. "Why did you lie? You got nothing on. Not a single case."
"That's why the wall took a pounding." Kate throws in.
"Why did you tell your brother you were busy?"
"Why shouldn't I?"
"Oh." John nods and looks at Kate.
"Nice." She says rolling her eyes and leans back against the sofa.
"Sibling rivalry." John signs.
"Now we're getting somewhere." Kate says sarcastically.
Before Sherlock can answer his phone rings and he picks it up. His face lits up and after he ended the call he immediately gets up. "Lestrade. I'm being summoned. You're coming?"
John gets up and follows Sherlock. A few seconds later they return and look at Kate.
"Me too?" She asks surprised.
"Obviously?" Sherlock says as if it's as clear as the fact that the earth goes around the sun.
"But I'll need my painkillers for that." She says while John helps her up from the sofa.
Sherlock's already downstairs getting a cab for them.