Sherlock Holmes was unequivocally happy. Escaping an inevitable death had shone a light on his affinity to London and everything that resided there. He was smiling, tweeting, finding joy and excitement in even the most basic cases that came to his door. He was revitalised; exuberating life in a way he never had before.

In 221B, John sat at the table typing up his latest blog post while Mary wandered the flat cradling her large stomach. Sherlock stabbed his knife into a large pile of letters on the mantelpiece.

"If this gets any better, I'm going to get two knives," he said as he sat in his armchair.

Vaughan climbed up onto his father's knee. Sherlock tickled him playfully.

John smiled. "It pays to advertise."

"So, what about Moriarty, then?" asked Mary.

"Oh, I have a plan. I'm going to monitor the underworld – every quiver of the web will tell me when the spider makes his move," said Sherlock as he typed out another tweet on his phone.

John stopped typing and turned to his friend. "Basically, your plan is just to sit there solving crimes like you always do…"

Sherlock grinned. "Awesome, isn't it!?"

He jumped up from his chair and flung his son over his shoulder as he walked to the mantelpiece and ripped a letter from the pile. The toddler squealed and giggled as he kicked his legs and swung his arms.

"Shall we go on a case?" asked Sherlock.

"Yes!" Vaughan shouted.

III

Margaux smoothed down her hair and straightened her blouse as she stood with her back against the wall. She fiddled with her I.D card, clipping and unclipping it to her trousers nervously while she waited.

Greg Lestrade turned the corner and hurried down the corridor towards her.

"Sorry, Margaux. Shall we?" he gestured to the door behind her.

She nodded and followed him. The meeting room was bursting with people; from uniformed officers to suited detectives. Their eyes trailed her as she made her way to a free chair.

"Okay everyone, thank you for being here. Sorry I'm a little bit late, we've just had a case called in so I'm going to make this quick," said Greg. "Right, before we get started with today's briefing, I wanted to introduce you to the shiny new member of the force, Dr Cave. She'll be working as part of our Scientific Intelligence Unit." He gestured to her. "Margaux, you want to tell them about yourself?"

"Sure," she nodded. "Er, hi, everyone. Yeah, my name's Margaux. I'm sure a lot of you may recognise me as I was a forensic investigator for many years. I assisted on a lot of cases for you guys here – which is basically what I'll be doing now except Scotland Yard's signing my pay checks instead." Everyone chuckled. She relaxed slightly as she continued. "So, a little about me: erm, I have a PhD in forensic psychology, went straight into working as an FI after Uni. I took some time away from that for a couple of years and did some teaching at the University of London, until my most recent work for MI5… which I can't discuss," she smiled, clasping her hands together on the table in front of her.

"That means it was actually MI6," said one of the officers.

The room mumbled with laughter.

"I can neither confirm nor deny," she said plainly, causing the room to silence – no one quite knowing if she was joking or not.

Lestrade completed the briefing and dismissed everyone, catching Margaux before she left the room.

"Fancy coming to a crime scene?" he asked.

"Are you asking me along for the ride, or am I actually needed?" she joked.

"It's a homicide. Murder-for-hire. But I mean, you could stay here and get a head start on your paperwork."

"I'll go get my coat."

III

They walked through the abandoned warehouse, their footsteps echoing against the tall, metal ceilings. Margaux parted the opening of the crime scene tent and stepped inside as she pulled on a pair of blue rubber gloves. Her brow furrowed as she assessed the scene in front of her.

"I thought you said it was a murder-for-hire?"

"That's right," said Lestrade. "We've got the victim's ex-wife in custody. She's just admitted to hiring someone to kill him. She said she changed her mind but the guy said it was too late and wouldn't let her call it off."

Margaux circled the body on the floor. "Well then someone else must have got to him first, because there's no way this was a professional job."

"How can you be certain?"

"Because–"

"Because nothing about this case is consistent with a professional murder," Sherlock interrupted as he stepped into the tent with Vaughan in his arms, a deerstalker hat sitting too big atop the toddler's head.

He was covering Vaughan's eyes with his hand as he continued to speak. "The murderer has attempted to conceal the body, albeit poorly, in the hopes that it would not be found. A hit man would not do that. Professional killings are quick, clean, precise, confident; they wouldn't go to the trouble of hiding a body when they don't need to. But you're a detective, Lestrade, you already knew that," he added sarcastically. "The amount of injuries, both superficial and fatal, indicate overkill. This man was murdered with rage, passion and opportunity. It's clear this was someone's first murder, but the fact that it was done through compulsion – a need to kill, tells me they will most definitely do it again, possibly escalating to spree killer status."

Lestrade scratched the back of his head and looked around the scene again, suddenly feeling like an idiot.

Sherlock had an excellent way of making people feel stupid. He rather enjoyed it.

"Sherlock. Outside. Now," said Margaux before storming out of the tent.

As she walked across the warehouse floor with Sherlock in tow, groups of officers began to gawk.

"Did Holmes just leave the scene with a kid?" one officer asked another. "I swear there wasn't any kids in there before."

"No, you idiot, that's his kid," said the other. "Holmes and Cave, they've got a kid together ain't they."

"Really? Wow. Remind me to give him a high five when I next see him."

"He doesn't even know you exist."

Margaux turned on her heels and took Vaughan out of his arms.

"What are you doing here?" she asked through gritted teeth. "We only just got called out an hour ago!"

"The victim's ex-wife sent me a letter. After failing to call off the hit, she requested my help."

"But this wasn't the work of the hit man. So why- no, how are you here. How did you know?"

"Well I first began–"

"Actually, shut up, I don't care. What I should be asking is why the hell you brought our son to a crime scene!"

"I'm babysitting," he said matter-of-factly.

Margaux growled before composing herself quickly. "Firstly, you're his father. You don't 'babysit'. Secondly, this is ridiculously inappropriate, unprofessional and dangerous," she hissed. "It's funny how he never winds up around dead bodies when he's with me."

"That's why I'm the fun parent."

She handed Vaughan back to him, the deerstalker slipping over his eyes.

"Take him home."

"But the case…"

"I'm assisting on this case. You know, because it's my actual job." She fixed Vaughan's hat and kissed his cheek before walking away. "Go home."

Lestrade burst out of the crime scene tent with his phone in his hands. "We've got a situation," he said. "Another body's been found about 30 minutes away."

Margaux turned to Sherlock who was smiling smugly.

"It seems my deductions were correct. But are any of us really surprised?" he said.

III

She climbed into her car and took a deep breath when suddenly, the back door opened. She looked in the rear-view mirror to see Sherlock strapping Vaughan into his car seat.

"What are you doing!?"

he shut the door and made his way around the car to the passenger side, climbing in and sliding the seatbelt across his chest.

"Didn't you hear Lestrade? Another body's been found," he said.

"Ugh, you make my blood boil," she said before turning her key in the ignition and beginning to drive.

"It seems I possess a lot of power over your body; I can make your blood boil, your toes curl–"

She sneered at him. "You know, at first I liked this new 'happy' Sherlock. But I've got to say, I'm starting to think he's an annoying fuc–"

Sherlock cleared his throat. "Margaux, there's a child present."

"Oh, don't you dare. You can't tell me how to act around my child when you've literally brought him on a day out to look at murder victims, like some sick Sherlock Holmes safari."

"Perhaps I misjudged the ethical implications."

Margaux laughed. "That's an understatement."

III

He sat at the table typing furiously on his laptop. The wet January night made the windows look like thick slabs of black glass, speckled with gold glitter as the streetlights shone through the rain. He stopped working as the sound of a car pulled up on the street outside. He walked to the window and watched as Margaux locked her car behind her and hurried inside.

"I saw on the news that they caught him," he said as she walked through the door.

She took off her wet coat and shivered as her cold skin met the warmth of the flat.

"Yep. I'm shadowing his interrogation tomorrow morning to see if there's any remorse–"

"There isn't."

She glared at him before continuing. "They just want someone from the SIU to be there, to make sure his solicitor can't get away with using an insanity plea. And since I accidentally ended up on the case today, I might as well be the one to do it."

She kicked off her shoes and ran her hands through her damp hair as a large yawn forced its way out. Sherlock watched her closely; it didn't take deduction to know she was exhausted.

"You are welcome to spend the night here if you wish. You can share my bed with Vaughan. Mrs Hudson just changed the sheets in the spare bedroom so I'll–"

Margaux began to laugh.

"What?"

"You," she said. "With this 'spare bed' thing again."

He rolled his eyes and walked to his armchair. "This again."

She got up and made her way to the chair opposite. "This again? Can you blame me, Sherlock? There was a part of me when you came back from the plane that really thought this was it. You know, we've been together before, but the night before you left… How could you possibly dismiss that?"

"I'm not dismissing it."

"Sherlock… You were there, right? You saw how easy it was for us to… be like that."

"Yes. But that's the problem; it would be extremely easy. And I can't afford to allow myself to become distracted. Not now, not with Moriarty–"

"Distracted?" she laughed, sitting back in the chair and crossing her legs like a child. "We have a son together, we see each other almost every day, you've probably memorised the number of freckles on my arse – don't you think it's a bit too late for that?"

"Relationships require a different level of effort and attention; two things that must be given willingly. I've never committed myself to anything like that before. I'm not entirely certain that I'm even capable. Also, seven."

"What?"

"You have a cluster of seven small freckles just–" he began to point.

"Hey!"

"You know you've not exactly expressed any direct intent to be monogamous with me either. There was barstool guy, hen night man, Dr Creepy…"

"Because I… I don't know either, Sherlock. You frighten me."

He looked at her with a heavy brow, as if the idea that he could scare her was too dreadful to bare.

"Not literally." She reassured him. "I mean… yeah I've had boyfriends; some more serious than others. But ultimately, I've always been alone; never relied on anyone, never let anyone in. You frighten me because when I'm with you, I feel vulnerable. Like you could really bloody hurt me. And you've proven that you can. Yet I'm still here. That's never happened before."

He didn't know what to say. So, he didn't say anything. Instead he sat quietly, watching her as she leant her elbow on the armrest, propping her head up with her fist. He watched as her blinks slowed down, her lips full and puffy as her face smushed against her knuckles.

"I'm sorry I intruded today," he finally said.

"It's okay," she replied, her voice croaky and tired. "You're a consulting detective, it's what you do. Just… maybe next time, leave the baby with John or Mary?"

He smiled, a gentle laugh escaping his nose. "I'm sure they'll appreciate being handed a toddler when they have a new born baby."

"Oh, they'll love it."

He paused for a moment. "What do you think of the name 'Sherlock' for a girl?"

She forced her heavy eyes open to look at him more clearly, thinking for a moment. "Yeah, I think it's kind of… sweet." She finally said.

He grinned proudly.

Sherlock watched her eyes close, her breath slowing calmly as she drifted off in her chair. He liked how she looked when she slept - with parted lips and soft cheeks. He would never tell her that though. He couldn't tell her that.