Well this is it, the beginning of the last episode of Sherlock. There are finally two chapters left not counting this one: the next, and an epilogue.

It's taking me very long to find a way of making the pieces fit together without having to hammer them, but I think I've kind of done it.

These chapters will be distressing. When I was writing them, specially the next, there were a couple of times I needed to stop and gather my bearings.

I hope you like it, I hope the way I've introduced magic into this part of the story makes sense, and that it fits the narrative. Enjoy! And do let me know in the comments, it would mean the world :).

The Final Problem - Beginning

'The stage is set, the curtain rises... we are ready to begin'

Sherlock and Mycroft have another sibling.

Hermione stared at the words for the hundredth time since getting the message the day before. It had given her a good distraction from the task at hand, but it had only delayed the inevitable. Hermione sighed, and with her phone in one hand and the tiny leaflet with instructions, she set the times to three minutes, left the phone on the counter and sat on the edge of the bathtub.

It wasn't far-fetched that Mycroft Holmes had hidden a sibling from everyone. Hermione had known from the very first moment of knowing Mycroft Holmes he was a man with many secrets, and as their professional relationship progressed, she had learnt he used his power and influence to protect them. One of the things that made the eldest Holmes so lethal was exactly that: he was ruthless, in whatever scenario. He managed everyone around him with surgical precision, disclosed the bare minimum, and rarely bothered with everyday business unless required. He was the master puppeteer, which gave him and his secrets an extra layer of protection.

Hermione glanced at the phone. Two minutes.

Mycroft had a lot of secrets, but power was a lonely business and trustworthy people, rare. And Hermione had filled the place some other people could not take - Sherlock because he was too busy getting high, colleagues could be potential enemies, parents were too much or not enough. He had revealed parts of his life to her, and in exchange Hermione had told him things that wouldn't be included in her magical report. Hermione still remembered the first time she had been properly told about Sherlock's existence - although there were all kinds of rumours if you went for that sort of thing. It had been a 'danger night'. Hermione had been blissfully unaware of what it meant, and Mycroft had poured himself and her a bourbon while he explained. Then he told her about Margaret and Siger, about Rudolf's long shadow, about Sherlock and everything that came with him. Mycroft would relay no information about work to her, unless necessary. But discussing family had never been an issue between them. Months ago, Hermione would have dismissed the news as ridiculous, but recent times had her thinking otherwise. She had been pondering the message over and over again, without reaching a conclusion. Every secret Mycroft held dear had something to do with his family. It was one cornerstone of his personality, despite how much he insisted on sentiment being a handicap. If there were something he would protect with his life, it was family.

One minute.

But Sherlock was not Mycroft. Mycroft could have hidden a sibling, could have gone as far as removing any mention of them from the files. But Sherlock was not power hungry, Sherlock had no reason to hide a sibling. And Sherlock had referred to Mycroft as his only brother on different occasions. To her mind came a little girl singing and a boy in wellies. She had thought they were a by-product of Sherlock's drugged brain, and he had appeared genuinely clueless about who they were. If the sibling existed, Sherlock must have known, Hermione decided. How could he not?

The alarm went off. Hermione took the stick in the sink and looked at the small window display. Her heart, faster with each beat, travelled to her throat, making her nauseous as the full meaning of the two pink lines sunk in.

The muffled music coming from Mrs Hudson's flat was the only thing that could be heard around the living room. Mycroft had been forced into the client's chair while John and Sherlock took their usual seats, forming a united front against him: John was the accusation and Sherlock, the judge. Mycroft closed his eyes briefly. He envied Sherlock's ignorance. As questions came, memories started to come unbridled, as they often did, and he had to make an effort for words to leave his mouth.

'Eurus was different from the beginning. Our abilities were professionally assessed more than once. Sherlock was clever, I was remarkable, but Eurus... She was described as an era-defining genius beyond Newton. We thought that was all she was. A genius.'

'What do you mean?' asked Sherlock.

Mycroft straightened in his seat and felt the impulse of defending himself. 'You need to understand, Sherlock. Neither of us had all the information we have now, it was impossible for us to k—'

'Mycroft, what happened to my sister?' barked Sherlock. His outburst when Mycroft had requested for John to leave was proof that under the detective's cold façade and tricks there was a bubbling rage Mycroft had never fully witnessed, and it could explode with the tiniest incentive.

Despite how angry he was still at John Watson—for everything —Mycroft was grateful for the calming presence he was.

'Eurus knew things she should never have known, as if she was somehow aware of truths beyond normal scope. It started when she was around three. There were minor things, at the beginning: she went to the door before anyone would knock on it, she warned us when it was about to rain. With time, it evolved, and she became quieter. Sometimes she would stare at you in silence like if you were a book she was reading. Once, she looked at me with those vacant eyes, and said that I looked funny grown-up.' Mycroft blinked. 'No one cared for these random moments, but I never forgot them. I only understood them years later, when I met Millicent Bagnold years later, shortly after Rudy died. But the damage was already done.'

'Who is this Millicent Bagnold?' asked John, trying to write everything down.

'She was the Minister for Magic at that moment.'

'Hold on,' said John. 'Your sister is a witch?'

'No. In a way, things would have been easier if she was.' Mycroft turned to Sherlock. 'Eurus is some kind of clairvoyant, without magical powers. I think the correct term is "seer". She only has images in her head that do not correlate to the reality she is living in. I believe she can now control them, but you can imagine what kind of sequels they can leave in a child's brain. As I've said, we found the explanation too late.'

'Magic? Is that why I don't remember?' asked Sherlock.

Mycroft shook his head. 'Magic was just the trigger.'

'What happened then?'

'Musgrave, where there was always honey for tea and Sherlock played among the funny gravestones with the dates all wrong.'

Sherlock closed his eyes and started whispering. 'Help succour me now...'

'... the East wind blows.' Both brothers finished together. 'You are starting to remember.'

'Just fragments,' Sherlock's eyelids quivered as his eyes moved under them. Suddenly, he opened them. 'Redbeard.'

'One day, Eurus took Redbeard and locked him up somewhere no-one could find him. She refused to say where he was, she'd only repeated that song. Her little ritual. Despite how much we begged, she never said anything, and we never found him. She started calling him drowned Redbeard, so we made our conclusions. Sherlock was traumatised and changed. In time, he forgot about Eurus.'

'How? They lived in the same house,' John pointed out.

'They took her away.' Mycroft stood up and walked to the window. Looking at the other side of the road, he did not see the mid-century building. Behind his eyes columns of angry orange and black were leaping at window frames, engulfing everything in raging hell. He turned to John and continued. 'Soon after Redbeard, she somehow got hold of a matchbox. Musgrave was an old house, all stone, and wood, and the quilts mother used to have. We had just enough time to take ourselves out before the fire consumed all the upper floor. The Holmes left Musgrave to never come back, and Eurus had to be taken away. Eventually, she started another fire, one she did not survive."

Sherlock turned to John and pointed to Mycroft. 'That's a lie.'

John looked towards Mycroft, who hesitated for a moment. 'Yes. It is also a kindness. This is the story I told our parents to spare them from further pain.'

'And no doubt to prevent their further interference.'

'That too. Uncle Rudy had a parade of the best psychologists in the world go to see her, and not one could get a word out of her, nor a reason why she had done it. Once I discovered what the affliction of our sister was, I tried again with another kind of... professionals. She has somehow rationalised the visions, and doesn't acknowledge them as such. The depth of Eurus' psychosis and the extent of her abilities couldn't hope to be contained in any ordinary institution.'

'Where is our sister, Mycroft?'

'There's a place called Sherrinford: an island. It's a secure and very secretive installation with the sole purpose to contain what we call 'the uncontainables.' The demons beneath the road - this is where we trap them. Sherrinford is a fortress in the middle of the North Sea with the most advanced technology and the most powerful magic, built to keep the rest of the world safe from what is inside it. And Eurus hasn't left - not for a single day.'

'That'd be 20,6. Normally vitamin B6 alleviates the symptoms. The first three months are the worst. By month four, they are usually gone.' Hermione forced a smile while fishing for her debit card inside of her bag. The assistant finished putting the different boxes inside of a white paper bag and looked at the flowers Hermione had left on the counter while paying. 'Those are gorgeous!'

'Thanks, they are for a friend.'

At the same time, she was getting the card closer to the chip and pin machine, she felt how the hairs at the nape of her head stood up and turned around. On the other side of the shop, a bushy-haired woman wearing thick-framed round glasses and big fashionable headphones seemed to be very interested in the lube aisle. Hermione stared at her, thinking she had seen her before. In the scarce two minutes it took to get her shopping and her bouquet leave, the uneasiness of being watched accompanied her to the exit. Even in the cemetery, when she left the flowers next to Mary's name, the feeling had not gone completely.

Hours later, Hermione stood up from kneeling in front of the toilet. She was panting from exertion, and her stomach hurt from all the dry heaving. She had barely made it back when her body had rebelled against her. She pressed her forehead against the cool wall tiles. She felt weak and exhausted. Her phone rang again, and this time she mustered just enough energy to drag her feet to where had dropped her bag when she entered home, next to the front door. The phone had stopped ringing, but she still picked it up and rummaged inside it. Dozens of messages crowded the lock-screen. Before she could unlock it, she saw an incoming call from Greg.

'Hermione, finally! Are you alright?' said the detective as soon as she took the call.

'Why wouldn't I be?' asked Hermione, confused.

'Haven't you seen the news? Baker Street has blown to pieces.' Hermione rushed to turn on the TV. On the news, a journalist was in front of 221, right in front of the police tape. Various police cars gathered around. The upper flat's windows were blown off, and debris was everywhere on the pavement and road. The front door had been smashed open and was now hanging by the hinges. Greg continued. 'Mrs Hudson called me. We found her at the back, with small cuts and bruises, but she is fine.'

Hermione lowered the volume, and started looking around for her keys. 'Was she alone? Where's Sherlock?'

'She has refused to talk to anyone, even to me,' he answered, a hint of annoyance covering his words. 'I think she might be in shock.'

'Can I talk to her?'

'Yes, hold on.' Hermione heard several people talking and the odd siren going off over Greg's half-hearted attempt of covering the speaker. Different noises filtered through, and finally, a breathy sigh.

'Hermione? Oh, dear, I've been so frightened!'

'Mrs Hudson, how are you? What happened?'

'I'm a bit shaky. I was cleaning, and then Mycroft appeared out of nowhere, grabbed me and took me to the back before everything exploded. Oh! I've been awful to him...'

'Did he say anything?'

'He told me not to say anything to anyone until I could talk to you. I think Greg might be crossed because I haven't told him anything—'

'Mrs Hudson, please, focus, this is important. Where is Mycroft now? And Sherlock?'

'I don't know.' The woman stifled a sob. 'They haven't found bodies inside of the flat, so Sherlock and John must've left somehow.'

Hermione gave Mrs Hudson a few comforting words and told her to do whatever Greg told her to. Martha bid Hermione goodbye, and Lestrade took the phone.

'Well, what do we do next?' said the inspector after Hermione had retold him what Mrs Hudson knew.

Hermione bit the inside of her cheek, trying to think. Everything felt like a

'Our monsters have been waiting for a very long time.'

'Do not dig into Sherrinford.'

'Moriarty's magic trick is just the beginning.'

'Greg, who knows about what happened inside of the flat?'

'Two of my forensics who did the sweep and Donovan. And then you and I.'

'Keep it that way. No, let Molly know, we need her safe. Send a brigade to her house, Rosie must be with her. Don't let anyone in, and wait for my call.'

'Hermione,' Greg had lowered his voice. 'How serious is it?'

'I don't know. I'll call as soon as I can.'

Hermione had never got dressed faster than that day. Her brain was working at an unforgiving speed, revising every interaction with Mycroft she had ever had. If all of this had anything to do with Sherrinford as she suspected, there was only one woman that would know.

Working for Mycroft gave her a special position, Hermione knew. Yet, it was only at Mycroft's request and invitation that she had been able to reach the underbelly of the beast that were the MI6 offices. Today, she had neither. As she approached the main gate and handed in her identification, she hoped her credentials got her far enough to attract the attention of the right people. Without a word, a guard escorted her inside the building, and led her deeper and deeper underground. The first part of the trip she knew: they were the same buildings she took to go to Mycroft's office. But then the guard took a left turn instead of right and passed a set of metal doors, which she had never seen before. On the other side, a short corridor led to an opening in the wall, from where Anthea was emerging, a deep frown set on her face. She went to Hermione and extended her hand as she usually did, silently asking for her mobile phone. With Hermione's phone safely in her hand, she left, and Hermione entered the room, followed by the guard, as saw the woman behind the desk.

'I was waiting for you.' Lady Alicia Smallwood irradiated power in a very similar manner to Mycroft. She had that aura of superiority and authority that was a hand-me-down from a position of privilege, something you learn since you are very young. As Mycroft, she had been primed for this position, and her late husband's famous surname had only helped her. Her office was a mirror of Mycroft's as well; the same disposition of furniture, that same portrait of the Queen hanging on the wall at her back. The only items out of place were a pair of pearl earrings on the table reflecting the yellow light above, an old Blackberry and a single piece of paper. Alicia gestured for Hermione to sit down and the guard left, closing the door behind him. 'My men haven't been able to go past Detective Inspector Lestrade.'

'This is hardly his first time. I promised I would call him with the official statement.'

Picking up the sheet, Smallwood read out loud. 'Mycroft Holmes' condition is critical, and he is being treated for his wounds. Sherlock Holmes and Dr Watson's whereabouts are unknown.' Alicia pushed the blackberry towards her. 'Use this. It's a secure line.'

Under the attentive stare of the woman, Hermione dialled Greg's number and relayed the information. She made him repeat it back to her, and when he was about to ask for more information, Hermione scrambled to say a quick goodbye and hang up the phone. Alicia took a metal box from one of the drawers and put the phone inside, and locked it.

'Now, Agent Black. What do you know?' Alicia fixed her eyes on Hermione.

'I don't know much. A bomb went off. Mycroft got Mrs Hudson outside before it, and then he disappeared, but no one has seen Sherlock and John. I can only make conjectures.'

Alicia regarded her for a couple of seconds, no doubt, trying to decide whether Hermione was hiding something from her, and sighed. 'It will be at least a couple of hours before our forensics team can get anything if those dimwits of Scotland Yard have not destroyed delicate evidence. Thank you, for getting us through to detective inspector Lestrade. You can go home now. Keep an eye on the phone, and if they contact you, let us know immediately.'

'With all due respect, Lady Smallwood,' Hermione said, 'I'm one of your best agents, I th—'

'You are. You have also proven to be reckless and impulsive when Sherlock Holmes is concerned. You are as it stands, compromised, and therefore, not suitable for the current situation. Now please, I have a lot of work to do.'

'I honestly thin—'

'I am not Mycroft,' said Alicia. 'I will not put people at peril just because you are too stubborn to accept an order.'

Hermione gaped at Lady Smallwood and stood up, leaning over the desk. Behind her, a security guard had entered the room and was cocking his gun. Hermione could feel the metal barrel pointed in her direction. The other woman held her gaze, apparently not intimidated by the invasion of her personal space. 'I know them better than anyone!'

'You don't know enough.'

One of the guard's hands closed around Hermione's bicep and started dragging her towards the door. The witch tried to turn around, but the man was too strong. 'Sherrinford!' Hermione shouted, in a desperate attempt to get Smallwood's attention. The guard stopped, and Hermione saw a flicker of surprise crossed Lady Smallwood's features.

'Where have you heard that name?' she asked once they were alone again. 'I know Mycroft has not told you. How do you know about it?'

'Mary Watson,' answered Hermione. 'You really must invest in better security. It took very little for her to break in and find all the information about Uncle Rudy's house of horrors. It's somehow Sherrinford involved in this?'

'What makes you think so?'

'I know Mycroft. He's been waiting for something to happen since Moriarty's face appeared across the country, saying his demons were coming to get him. Not to mention, he tricked an assassin into killing Magnussen because he had something on him that he did not want anyone to know.'

'How much do you know about Sherrinford?'

'It's a fortress, designed to contain the most dangerous people on earth, very top secret as Mycroft told me not to dig into once he knew I had found out about it.' The other woman let out what looked like all the air in her lungs. Hermione understood there was something else she was missing. 'Is that where they are? What else should I know?'

'You must understand, Mycroft has gone to great lengths to keep Sherrinford out of the public eye. I can't tell you this kind of classified information.'

'Mycroft Holmes, Sherlock and John are missing. Whoever has them literally has the source of classified information. If whatever I don't know about Sherrinford is going to help us find them, I think it's worth risking an enquiry.

Alicia Smallwood nodded and turned around, facing the Queen's portrait. She dragged her long fingers along the underside of the frame. There was a soft click, and the painting dislodged from the wall. The safe behind it was also a replica to the one Mycroft had. Alicia scanned her fingerprint and took a thick file out. She handed it to Hermione. 'I have the dubious privilege of introducing you to Eurus Holmes.'

Sherlock and Mycroft have another sibling. Hermione opened the first page and saw a very familiar face looking back at her. It might be her eyes, so much like Sherlock's, it would have taken her a few instants to distinguish them from his. But Eurus eyes seemed vacant, and where Sherlock resembled clean water, Eurus were more like stone, cold and hard.

Alicia sat back down. 'I think I owe you an explanation. Well, Mycroft does, but we'll have to make do. Eurus Holmes is, as we speak, an inmate at Sherrinford.'

Alicia then started a tale that could have been the making of a bad Sunday telly film if it wasn't because it was true. A drop of magic ran in Holmes' blood, and it had resurfaced in a seer. Now so many things made sense.

'So why is she exactly at Sherrinford? Why not in a normal facility?'

'She is a Holmes, after all. You can only deduce what kind of mind she has. Her abilities... There's no one like her. Her brain is unique, and Mycroft thought she could be useful for some more... delicate cases.'

'He uses his brother as well. He uses everyone.'

'You disappoint me. I thought after all this time, you had some understanding of how Mycroft Holmes chooses to show affection.' Alicia snickered. 'I always forget that no matter how much Mycroft has taken under his wing, you were never here when things were really bad. Cases were for a very long time the only way of reaching out to Sherlock, and this was the only way to be in contact with Eurus. We all saw her for what she was, either a useful tool or an incarcerated monster, but I underestimated the depth of Mycroft's feelings for her. It never occurred to us that for Mycroft, she was his little sister. I warned him, but he did not listen. He was not wrong, she was useful, but the price to pay was too high, I see now.'

'What do you mean?'

'Five years ago, Eurus requested to have a conversation with Moriarty. Unsupervised, five minutes.'

'Adler said Moriarty had met someone five years ago and had started to plan his final game.' His muse, he had called her. A shiver ran along her spine. She had never met Moriarty, not in person. Mycroft had tried to expose the least amount of people to him as possible, but she had dealt with the aftermath. A criminal mastermind, and a genius without morals.

'We thought five minutes would not be enough to plan anything, but it was. Magnussen knew, probably Moriarty told him at some point. When they died, it looked as if all the loose ends had been cut. But then Moriarty reappeared. Mycroft has kept tight monitoring of her since then.' Alicia Smallwood glanced at the box with the phone inside. 'I've been trying to contact the Governor, but they are not picking up. He has strict instructions to always pick up when this extension calls. And Mycroft has not contacted me either, so it's time to assume the worst.'

The siren was supposed to be loud enough to be heard all around the thousands of square feet the prison had. Inside the Governor's office, it blended with the sound of armed guards storming through the glass doors at the Governor's command. Mycroft looked to his left, where John was in the same position he was: his arms held high, three semi-automatic rifles pointing at him. Somewhere, Sherlock had been left alone with the woman controlling the place, and that scared Mycroft more than any weapon. They were hostages now, and about to be forced into whatever sick game his sister and Moriarty, now playing through the speakers, had devised. When John broke off in a foolish move, Mycroft saw his opportunity. He rubbed his thumb on the ring he always wore, feeling how it heated up against his skin.

Again, he was asking too much.

Hermione felt a burning sensation in the inside of her wrist. In there, a small feather pulsated against her skin, the thin black ink traces bulging and twisting. The feather had been drawn years ago, but now it served a different purpose.

'Mycroft is alive, but he is in danger.'

"I thought we had already ascertained that."

Hermione thrusted her arm over the table. Lady Smallwood wrinkled her nose when she saw the skin moving. 'This is a distress signal. Mycroft's ring and my tattoo are linked, and when one of us makes a specific pattern over our part of the link, the other heats up.'

'I always wondered about that ring,' commented Smallwood. 'Could it have been activated by mistake? Or could someone have taken it?'

'Mycroft cannot take the ring off, the only way for the ring to leave his finger is by chopping it off." Hermione swallowed hard. 'And Mycroft is too careful. If he's activated it, he must have a reason. They have a huge time advantage, but if we can get a helicopter—'

'Hermione,' Smallwood interjected, and Hermione was surprised to hear her given name. 'I am not exaggerating when I say Eurus Holmes is the most dangerous person in Britain. By now, the prison and the surrounding water are probably under her control. We have no visual, no inside information, and the last update was hours ago. Right now, sending a team there is probably sending them to their deaths.'

'What are you saying?'

'We need to call a crisis cabinet. There's more at stake than three lives, and I am afraid that, in the bigger scheme of things, Mycroft, his brother and Dr Watson, they do not rank very high in the list of priorities. Mycroft would have understood this.'

'I CANNOT BELIEVE IT!' Shouted Hermione. 'Are you going to leave them there with a psychopath?'

'I've told you already, I am not going to risk any operatives until we have more information. And that's final.'

Hermion took a step forward. 'Then risk me.'

'You don't understand. The moment you step in that prison, you'd be alone at Eurus' mercy. And you cannot use your wand, the whole place has magic quenchers covering every inch. Well, except—' The older woman stopped for a second. 'The Governor's office is the only place where magic works.'

'I could apparate there. And I know how to handle a gun. This won't be any different to any other rescue mission. Just let me get in your memories, and I'll go.'

I have never been to Sherrinford. Mycroft keeps tight control over who is allowed there. I only know one person who's been to Sherrinford before.'

'Who?'

'Sirius Black.'

"Hello, my name is James Moriarty. Welcome, to the final problem."