The yellow door was now grey. Bleak and streaky. Sherlock looked at it with an air of disappointment.

"Are you not at all nervous?" John asked.

"Why would I be nervous?"

"Because you haven't seen the woman in two years."

"I hadn't seen you in two years and I wasn't nervous." Sherlock answered, his eyes still focused on the door.

"Yes. But the difference is, you and I weren't fuc–"

The door opened slightly, a woman with greying hair peered her head around. "Yes?"

Sherlock's stern, lifeless expression suddenly became charming and attractive. "Hi," he began with a smile, "We're looking for Margaux."

"I don't know a Margaux, sorry."

"Well this is her flat, is it not?"

"Well I've lived here for a year now so I don't think so."

Sherlock huffed.

They stepped out of the building onto the street, the sun was setting and the breeze was cold. Sherlock flicked up the collar of his coat and began to walk. John zipped his jacket up, shoved his hands in the pockets and followed.

"You were nervous," he jabbed.

"I wasn't nervous, will you shut up."

They knocked on three more doors around London, none of which held Margaux on the other side. Sherlock had come to realise that his sources had failed him.

"This would be a lot easier if she had family," he said.

"Ah yes, how dare she be emancipated from her negligent parents, to which she was the only child. How selfish of her to be all alone in this world," John replied sarcastically.

"You know what I mean."

"What about Molly Hooper?"

"Are they still friends?"

"I don't know. I would assume so," John guessed.

III

"We catch up every now and then. It's hard now with her not coming to the hospital to work anymore. But yes, we still talk," said Molly as she stood over a corpse with a scalpel in the morgue.

"Do you have her current address?" Sherlock asked, un-phased.

Molly hesitated. "I don't know if I feel comfortable just giving someone's address out."

"Come on, Molly, it's me," Sherlock said with a charismatic smile.

"Smooth," said John.

"I don't know–"

"Do you have it written down somewhere?"

"Sherlock, I really don't know–"

"You send Christmas cards every year, and you post them as opposed to hand-deliver which means you keep all of your contacts and addresses in one place. You're slightly messy and very sentimental, so the list is most likely in an old diary that you keep in your office- no, your car. No. Handbag."

"Sherlock," said Molly.

"It's an old diary, well out of date, but it's compact so you continue to use it," Sherlock continued as he walked towards Molly's bag. "She moved at least a year ago, and we've had a Christmas since then which means you have her new address, most likely written next to her old one, as I said: sentimental, can't bring yourself to cross the old one out." He reached into her bag.

"Sherlock, come on, you can't go through her bag," said John.

"Oh relax, what do you expect I'll find? She's not a weirdo or a drug addict or something."

"No that's just you," John quipped.

"There won't be anything personal or embarrassing, she's not due on her period for at least another two weeks."

"Sherlock!" Molly shouted.

He pulled the diary from her bag, flicked through the pages effortlessly and memorised Margaux's new address.

"Thanks." He winked.

Molly shook her head and sighed. He was infuriating.

III

It was time to try again. He adjusted his stance, his posture perfectly straight, his chin up. He placed his hands behind his back and waited.

"Sherlock, you need to ring the bell," said John.

"Hm? Oh." He stared at the doorbell, watching it intently but never moving his hands.

"Would you like me to press it?"

"Hm?"

"Oh for god's sake." John pushed the doorbell and stood back in the corridor.

She had moved thirty minutes away from her old flat. This one seemed bigger, Sherlock thought as he scanned the length of the walls between the front doors either side. He braced himself for a boyfriend to answer the door. It seemed the most logical deduction of why she moved.

They heard a chain rattle, followed by a click and a creak as the door opened slowly. There she was, standing on the other side; her smile suddenly evaporated as she laid eyes on them.

Sherlock smiled another rare, genuine smile. "Surprise," he said.

She walked slowly back into her flat, the two men following behind. She turned to face them in the middle of the hallway. She was barefoot, her hair tied in a ponytail, her face clear of makeup except the slight stain of whatever lipstick she had worn that day. She was wearing a jumper underneath a pair of well-worn dungarees. She seemed smaller, or perhaps Sherlock had just forgotten. There was silence among the three; John watched as the pair stood opposite each other. He saw the pain in Margaux's face, the confusion, the betrayal, and he recognised it all in himself.

Sherlock inhaled as if he was about to speak, "So–" but he was met by a hard, stinging slap across the face.

"You pretended to die," she said slowly and quietly. "You come back here after two years, knocking on my door uninvited and the first thing you say is 'surprise'?"

"I'm sorry," Sherlock whispered as he clutched his cheek.

After a few moments, Margaux rolled her eyes and sighed. "I better get you something for your face," she said indifferently.

She led them into her living room and gestured to the couch. The pair sat down. John felt something hard under his leg, he reached under the cushion and pulled out a small, plastic toy car. He placed it on the table next to him. Margaux handed Sherlock a bag of frozen vegetables wrapped in a tea towel, placing it roughly against his cheek.

"Congratulations," Sherlock said.

"For what?" Margaux replied.

"Your son. How old is he?"

John glanced at the car again, then around the room, now noticing the corner filled with toys, the tiny armchair next to the television and the basket of nappies and wipes tucked away under the coffee table.

Margaux cleared her throat, struggling to form a sentence. "He's um, he just turned one." She nodded.

"Well congratulations indeed," John began. "You and your other half must be over the moon."

"Uh, no other half. It was a one night sort of thing."

"She's lying," Sherlock said, leaning towards John who was sitting next to him.

Margaux pointed her finger at him, "don't you dare start." She turned away and began pacing the room slowly.

Suddenly, the living room door creaked open. For a moment, it seemed as though no one was there, until a soft voice whispered from around the back of the door.

"Mummy…"

Margaux's eyes widened. She went to him and picked him up swiftly, "What is it, love?"

The little boy looked over to Sherlock and John. He was fair skinned with soft, round cheeks and bright blue eyes piercing through masses of dark eyelashes. His hair was dark and wavy like Margaux's, just long enough to fall into his face. Margaux brushed it back with her hand, kissing him on the cheek.

"I not tired," he mumbled, rubbing his eyes.

"Oh I think you are," Margaux laughed.

"No, no, no, no," he started to shout.

Margaux shushed him gently. She looked over to Sherlock and John, and back to her son. She sighed.

"Okay, a few minutes."

She placed him on the floor and he ran quickly over to his toys, sitting down and beginning to play quietly. John's brows furrowed slightly as he watched the toddler play.

"What do you want, Sherlock?" said Margaux as she sat on the other couch.

"There's something I'm missing. Something that's tying two bizarre and dangerous events together. I need you to take a look."

Margaux laughed. "See, I thought it couldn't get any worse than finding out you'd died on the news. But then, two years later, I found out you were actually alive on the news too. Now the first time I'm seeing you, it's because you want my input on a case."

"Margaux," John interrupted distractedly, "how old did you say he was again?"

"Hm? Oh he's one."

"You said he'd just turned one?"

Margaux glanced between the two men. "Yes."

"Right."

"Look, Margaux, I'm sorry. I've said it to everyone, I'm sorry. I will explain everything to you but first I need your help." Sherlock was becoming distracted by drips of cold water onto his shirt and trousers.

"The bag's defrosting. Let me get you a different one," she said, standing up and taking it from him.

"Vaughan, mummy's just going into the kitchen, okay?"

The boy looked up at Margaux and nodded with a smile, before returning to his toys.

"Vaughan?" said Sherlock.

"Yes. What can I say? Unusual names run in the family," said Margaux as she left for the kitchen.

She threw the bag of vegetables back in the freezer and leant against the counter, covering her face with her hands. She let out a huge breath before reaching for the bottle of gin in the cupboard. John walked in, looking down at the bottle in her hand.
"Gin and Tonic?" Margaux offered.

"No thanks," he smiled. "Actually, go on then."

She poured two glasses of gin and topped them with tonic water from the fridge. John noticed her hands were shaking.

"He's been home for weeks, John." She looked over to him, tears forming in her eyes. "I'm not saying I was this big, important person in his life. But to not even cross his mind when he came back?"

"I don't doubt for one second that he's thought of you."

"Clearly," she scoffed. "And you. It's been two years; you didn't pretend to die, what's your excuse?"

"Hey," John began, holding his hands up. "I swear I tried to catch up with you. It was a couple of months after he… Well, I went to your work. They said you–"

"Yeah, I took paid leave for a few months and never ended up going back. Sounds stupid now that he's sitting in my bloody living room but, Sherlock's death… It changed things."

"Yeah don't I know it." John took a sip, "Where are you now then?"

"I lecture in forensic psychology at the University of London. Yes, I'm a teacher." She laughed into her glass. "It was just easier with having Vaughan. More 'sociable' hours; I can take him to nursery and pick him up again. It is better."

"Well he's lovely, definitely worth it," John nodded.

"Oh absolutely."

"And very clearly older than twelve months."

They looked at each other intensely, the silence growing uncomfortable.

"He's Sherlock's, isn't he." John finally said.

There was another long, empty silence. Margaux put her glass down on the counter.

"I was going to tell him the baby survived. Then he decided to go and die before I got the chance."

"Margaux…"

"Don't tell him, it's been too long now," she said quietly.

"Tell him? Margaux, it's Sherlock, it's only a matter of time before he bloody deduces it for himself."

"Well then there's no need to tell him, is there."

"Yes there is. He's sitting in there right now with his son and he doesn't even realise it."

"And I've spent the last eighteen months raising his son by myself; explaining to a baby that his daddy lives in a special place that we can't ever visit. Now he's suddenly back, and he's sitting on my couch, and you're saying I owe it to him."

"He didn't know, Margaux."

She leant on the counter again, rubbing her eyes.

"Fine. But I'm not telling him tonight."

She handed Sherlock a fresh bag of frozen vegetables. His face looked red and she felt a whisper of guilt forming in the back of her mind.

"Can I please just show you the footage?" Sherlock asked.

"Fine."

Margaux walked over and sat between them. He took out his phone and played the clip of the train.

"What the…"

"Exactly. Now where did he go and how is he planning on destroying London?" Sherlock placed the tips of his fingers together and rested them on his chin, watching her as she began to think.

"Jesus, Sherlock, I'm not a crystal ball."

Vaughan walked up to Margaux. She lifted him up and sat him on her knee. He gazed up at Sherlock, his eyes mirroring the ones looking down at him. Sherlock allowed a slight smile and patted Vaughan's head awkwardly. Marguax and John shared a glance.

"I've exhausted every inch of my mind palace and I cannot come to any sort of answer."

Vaughan turned and reached up to John, trying to touch the cuts on the side of his face.

"Oh, love, don't touch," said Margaux. "John! I didn't notice how bad they were."

"Yeah, got buried in a bonfire, as you do," he joked.

"A bonfire?" she laughed. "A bonfire," she said again, more seriously now. "A bonfire, Sherlock... Where did the man get on the train?"

"Westminster."

"How many carriages?"

"Seven…" Sherlock's eyes widened at Margaux. Hers widened back. Their silent conversations still blowing John away.

Sherlock stood up suddenly and began walking around the room, his movements excited, enthusiastic. "Oh that's brilliant. That's just brilliant. I've been a blind idiot!"

"Sorry?" John asked.

"Margaux that's it, you're right. Oh my god it all makes sense now."

"Hello? Normal person over here? Can you please explain?"

Sherlock loaded the video again, showing it to John. "Look, seven carriages leave at Westminster. But only six carriages arrive at St James's Park."

"But that's… It's impossible," said John.

"Lord Moran didn't disappear, the entire tube compartment did," Sherlock replied.

"The driver must have diverted the train and detached the last carriage." Margaux agreed.

"Detached? Detached it where? You said there was nothing between those stations," said John.

"That carriage vanished," said Sherlock, still pacing. "It must be somewhere."

"But why?"

"Lord Moran and a full train carriage disappears somewhere between Westminster and St James's Park," Margaux explained. "Around the same time, you're almost killed at a fireworks party. Do you see it yet?"

Sherlock turned sharply. "What's the date today?"

John looked down at his phone, "November…. Oh my god."

"Remember, remember the fifth of November," said Margaux.

III

"Tonight there's an all-night seating at the House of Lords to vote on the new anti-terrorism bill. Lord Moran won't be there," said Sherlock as he walked quickly through the dark streets.

John caught up at his side, "So what do we do now?"

"We need to go back to the flat and give the train guy another call. There must be something down there." Sherlock hailed a black cab. The pair climbed in. "Baker Street please."

Almost the entire cab ride was quiet. John could see the familiarities of the streets around him, they were close to home.

"So," John began. "Margaux. A kid. How do you feel about that?"

"How do I feel about what? How do I feel about seeing Margaux with a child? Or how do I feel about discovering I have a son?"

John almost choked on his own saliva. "You know?"

"Of course, John. She said the boy was twelve months old but his size and co-ordination place him clearly at eighteen months. Even then, he was still extremely advanced for his age; his ability to understand, comprehend and construct sentences, the clarity of which he speaks, his ability to play so intricately. All genetic." He gestured to himself. "Plus the fact that Margaux was so very obviously lying about having a one night stand, and he looked exactly like me."

John sat with his mouth open. "Sorry, is that it, are you done?"

"Also, she named the child Vaughan. Clearly a subconscious way of connecting him to his father; by giving him an equally unusual name."

"Why didn't you say anything?"

"Because I have the case to think about."

"Sherlock!"

"Okay, fine… I feel it is her right to be in control. It is up to her to invite me in."

"And if she did invite you in… Would you want to be… in?"

"I don't know."

III

They stepped onto the dark carriage tucked away in the forgotten underground station. They walked slowly from one end to the other, shining their torches, in the hopes that they would find something.

"It's empty. There's nothing," said John.

Sherlock's eyes zoomed in on the thin, red wire travelling down the walls of the carriage and disappearing under the seats. He ripped up the cushion to reveal rows of packages and wires taped underneath.

He turned to John, "this is the bomb," he said. "It's not carrying explosives; the whole compartment is the bomb."

The pair began ripping up every seat cover, revealing more and more packs and wires. Sherlock looked around, searching for an origin point, he took a few steps and noticed a loose piece of floor. He bent down and lifted the panel.

"We need bomb disposal," said John as he shined his torch on the large metal contraption buried in the floor.

"There might not be time for that."

"So what do we do?"

"I have no idea." The phrase sounded strange coming from Sherlock.

"Well think of something."

"Why do you think I know what to do?"

"Because you're Sherlock Holmes. You're as clever as it gets."

"Doesn't mean I know how to diffuse a giant bomb. What about you?"

"I wasn't in bomb disposal, I'm a bloody doctor."

"Soldier, as you keep reminding us all," said Sherlock, shining the torch in John's face.

They looked down at the bomb, noticing a digital display. It read '2:30'. Suddenly, the carriage came to life, illuminating and humming as if someone had flicked a switch. The display began to tick down; 2:29, 2:28, 2:27…

III

Margaux finished another small glass of gin, no tonic this time. She sat on the floor with her back against the couch, Vaughan was curled up, sleeping under a blanket just behind her. She looked down at the palm of her hand, it was red from where she had slapped Sherlock. She cupped the cool glass to ease it.

She had wished often for him to come back to life. Now that he was here, she realised she had forgotten how cold and emotionless he could be. She glanced back at Vaughan, fixing the blanket over his legs.

"What do I do?" She whispered.

III

John stood, eyes closed, bracing for the explosion. He was silent, breathing heavily, his thoughts turning to Mary and what could have been. He could hear Sherlock's sobs from the ground as he knelt over the bomb. Then he listened closer and realised he wasn't sobbing, not even whimpering, in fact, Sherlock was laughing. John looked down at the bomb. It had been stopped.

"You!"

"Your face," Sherlock laughed.

"You utter…"

"Your face!"

"You cock!"

"I totally had you."

"I knew it, I knew it, I knew you…" John began pacing, both relief and anger driving his movements. "I will kill you, if you ever breathe a word of this–"

"Scouts honour."

"To anyone! You knew how to turn it off!"

Sherlock bent down to the bomb. "There's an off switch, John. There's always an off switch."

III

He popped open a bottle of champagne and walked into the living room of 221B. He handed out glasses to Lestrade, Mary and Mrs Hudson as they talked amongst themselves.

"Ah a spring wedding," said Mrs Hudson to Mary.

"Yeah, you will be there, won't you, Sherlock?" asked Mary.

"Hm, weddings… not really my thing."

"Hello everyone," a voice came from the doorway.

Sherlock turned to see Margaux standing with Vaughan in her arms. Mrs Hudson and Mary stood up immediately.

"Oh Margaux, hello dear how are you?" said Mrs Hudson cheerfully.

"I'm well thank you, how are you?"

"Who's this!?" said Mary, gazing at Vaughan's rosy face and striking eyes.

"This is Vaughan," said Margaux, taking him over to them.

"My, aren't you just a dream, come here," said Mrs Hudson, taking him and placing him on her lap.

Mary smiled, "Hi, I'm Mary, John's fiancé. Well, that is if he ever asks me. We were interrupted last time." She shot Sherlock a glance, he grinned.

"Margaux, I'm… a friend," she shook Mary's hand.

Mary glanced at Sherlock again, this time she didn't have to say anything.

"Champagne, Margaux?" said Sherlock, diverting Mary's stare.

"Sure." She stepped over to him, taking a glass and watching as he filled it with such care. "Thanks," she said, taking a sip.

She took off her coat and unwrapped her scarf, holding them awkwardly over her arm.

"Here, I'll take those," said Sherlock.

He walked over and placed them on his armchair, she followed behind.

"So, you almost blew up?"

"Eh, I've been closer to death." He winked.

She couldn't believe his confidence. The night before he had received a hard slap for faking his own death, now, not even 24 hours later, he was joking about. A small laugh slipped out. It was funny. She couldn't help herself. They both took a sip of champagne.

Sherlock watched as Margaux glanced over at Vaughan. He had noticed she kept doing it, like an automatic tick. "It suits you, you know."

"Hm?"

"Motherhood."

"You haven't seen me at 3am on no sleep," she scoffed.

"Hmm, I believe I have," he replied.

She wasn't sure if he was completely aware of the joke he just made. She laughed and pushed his arm gently with her fist. Now he was looking over at Vaughan.

"Sherlock…" She began tentatively.

"I know."

"Wh–"

"I know," he said again, this time looking down at her.

He hadn't seen eyes like hers before, and never any since. He thought of her eyes during every golden sunset when he was away.

"Well I want you to know that I don't expect you to… Well, I mean I know you're not always…"

There was a long silence. He watched her as she gulped down the entire glass of champagne, her chest rising and falling rapidly with every quick, worried breath.

"May I introduce myself to him. Properly?" He asked.

"Is that what you really, honestly want, Sherlock?"

He shrugged. His jaw clenched as he looked over at the group fawning over the boy.

"It'll be fine," he said nonchalantly before stepping away from her and over towards the group.

She shook her head and exhaled. This was going to be interesting.