"Billy."

"Hey, Shezza," Billy stepped aside and let him enter, a half smirk on his face.

"It's for a case," Sherlock hissed through clenched teeth.

Billy nodded, still smiling. "It's alright, you know I don' judge. There's an empty space at the end of the second-floor hall. Watch out for the bloke wi' the black eye, though, he's in a right strop, he is."

Sherlock trod warily through the semi-darkness of the derelict house. The sticky sweet smell of smoke and the spicy tang of unwashed bodies hung heavy in the air. The room was crowded, but as Billy had promised there was an empty pallet in the far corner. Sherlock paid little attention to the glassy-eyed stares of the room's occupants as he settled onto it. They were of little concern anyway, he wasn't here to find a suspect. All the participants in this particular case were long since gone, considering the last crime had been committed over one hundred and twenty-five years ago.

It wasn't often he looked to the past for a case to solve. He saved that for times when there was nothing on and John was out of town. Like today. It was unfortunate timing that had both Lestrade away on holiday and John trekking out to Stoke on Trent to deal with Harry's latest relapse. The matter, of course, was complicated by the shortage of interesting inquiries to his inbox.

It was a great challenge to solve a case when he was forced to rely only on the insight of others. The Whitechapel Murders were something he had previously avoided due to the massive sensationalization of the events. He had done some extensive reading overnight and was ready to begin reviewing the data. The list of suspects was more abundant than his usual cases. Thanks to the solitude provided here he hoped to have a reasonable hypothesis by the end of the day, tomorrow at the latest.

"So, is John going to be away for long?"

He wasn't sure how long he had been submerged in his mind palace, but he suspected it had been several hours judging by the stiffness in his joints. As he slowly re-emerged into consciousness, he was aware of the change in his surroundings. The once crowded room was deserted save for two individuals snuggled up together nearest the door and a figure settled on the pallet next to his. Her face was half hidden in the shadows and a soft blue shawl was draped over her head, but he knew her. The four laptops surrounding where she sat only confirmed the fact that it was Sherrin. "Three days. Are you wearing a hijab?"

"Oh," she inhaled, then giggled girlishly as her hands felt the neatly draped fabric. "Yes, I guess I am. I didn't even realise I had done it. It's bloody cold in here and I pulled my shawl over my head to keep warm. I must have unconsciously tucked it into a hijab out of habit. I've spent a considerable amount of time in Turkey and Pakistan in the past. One has to dress accordingly when trying to remain inconspicuous."

"Yes, I know. I became very adept at arranging a shemagh several years ago in Pakistan." Sherlock stood and stretched before stepping nimbly between the laptops and taking a seat shoulder to shoulder with her. No sense wasting body heat when he had someone with whom he had no aversion to sharing the same space. She leant into him when he wrapped his arm around her shoulders.

"Oh? Tell me about it." she hummed, smiling when he placed a kiss on the top of her head.

"It was in Pakistan," he hummed back at her. "I was helping a… friend."

Sherrin turned her head to look up at him, "A, not John, friend?"

"Yes." Sherlock nodded, remembering the events clearly. "Although, calling her my friend may not be entirely accurate. She was more a minor adversary."

"A woman?" Sherrin smiled. Even if Mycroft had not told her an abbreviated version of Sherlock's encounter with Ms Adler in London, she had already heard the story of the woman's escape from death, from a Pashtun over tea only a few weeks after the event had played out. "The woman John talked about on his blog? You helped her in Pakistan? I think I might just remember hearing a story of an execution gone wrong. I seem to have forgotten the details, though."

Sherlock sniffed, bloody know it all. "You and I both know you have an eidetic memory. Don't pretend otherwise. Her name was Irene."

Sherrin raised her eyebrows suggestively, "Mycroft said she was a dominatrix."

"Oh, please, Mycroft says a lot of things. You know I am not interested in women in that way," Sherlock groaned. "Why are you here?"

She pulled her knees up and wrapped her arms around them, her earlier mirth replaced by a melancholic mood. It was several minutes before she answered. "I had to get away. I was tired of everyone trying to coddle me and wrap me in cotton wool. Mummy keeps asking me if I am all right and tries to make me eat. In addition, Mycroft keeps insisting that I should not have gotten involved in matters of the heart, 'caring is a disadvantage', he says. Daddy finally called Quentin and demanded he give me something challenging to work on. Then he faked an episode of chest pain so I could slip out unobserved."

"Beth, you could have called me," he said quietly.

"And what would you have done?" she eyed him sceptically.

"I would have dragged you away to Baker Street, bolted the door and made Mrs Hudson regale you with stories of her younger days and when you got bored with it, I would have taken you with me on a case. You would be an invaluable addition to my work."

Sherrin laughed and shook her head, "Not really my area, Lock. Besides, it's too people-y out there."

Sherlock frowned, " 'People-y'? Is that a pop culture reference or something? I am not familiar with the term."

"I'm not really sure of its origins, I like it, though," she shrugged. "What I am trying to say is that I want to be left alone, Sherlock. I deal with grief in my own way. I am perfectly happy sitting here and hacking into supposed impenetrable systems."

Sherlock looked over the four screens facing them, "Anyone I know?"

"MI5, MI6, the MOD and just for laughs Mycroft's personal laptop. M wanted me to test the country's vulnerability to cyber-attacks. I think he just wanted to see if I am as good as Quentin said I was."

"And Mycroft?"

"I was bored and he was being a tosser."

Sherlock laughed, it was amusing to see sibling rivalry at its best. "I hope you renamed all his files or deleted his calendar."

"I started to but then I decided to go for something more sinister. I configured the space key actually write the word 'space' every time it is pressed. And when he corrects that, I have the computer set to load random web pages from popular baking sites. He should have cakes and tarts popping up on his screen every fifteen to twenty minutes."

Sherlock laughed and hugged her tighter. "That's my girl! Now, let's get you to somewhere warmer and you can tell me why both of us are sitting in a drug den and neither one of us is high, hmm?"

"All right, but only if you tell me who the real Jack the Ripper was."