Disclaimer: All the characters displayed in this fic are property of their respective creators, JK Rowling (Harry Potter), Moffat and Gatiss (BBC Sherlock), and Sir Arthur Conan Doyle (Sherlock Holmes).

Note 09/02/2021: Edited, unbetaed

His last vow: Act I, Introduction

The corridors in the north wing of St Bart's, unlike the main corridors, were empty at this time of the morning, except for a couple of nurses and porters. Hermione followed the signs in the direction of the pathology lab. In her pocket, her mobile vibrated again. Hermione was tempted to turn around and forget that John had texted her with a succinct 'Molly's lab. Now'. Especially since it didn't take a genius to know that the only reason John would be in St Barts on a Friday morning at nine o'clock, fresh from his honeymoon, was Sherlock.

Everything was about Sherlock.

Hermione took a right turn. As she approached the fire-safety door, she heard voices from the other side. She could make out John, and of course, Sherlock, arguing. Hermione took a deep breath and opened it. Everyone in the room turned their attention to her.

'Finally,' said John. Hermione looked away from John and instinctively searched for Sherlock, propped against one of the lab benches. He looked every bit the stereotypical junkie. The dirty tracksuit he was wearing hung loosely on him, and the pair of trainers on his feet had holes on the sides. His usually luscious curls were matted and greasy with sweat, and a thin scruff covered his chin and jaw. He looked thinner than the last time she had seen him, and more tired. He had barely raised his head to look at her, but she had caught sight of his face. His eyes were bloodshot, and his cheeks slightly sunken.

Suddenly Hermione understood why John had summoned her there, of all places. Sherlock was not only playing dress up as a druggie, but he had also borrowed their toys.

Hermione tore her gaze away. Except for the fact that she now had to get an STD test at her local clinic just in case, what Sherlock did, snorted, swallowed, or injected into his body was none of her business. From across the room, Mary gave her a tired smile as she bandaged the arm of a man possibly dug out of the same sinkhole where they had found Sherlock. Beside her, a young boy, no older than sixteen, wobbled in his seat—what an unholy trinity.

'Molly is going to analyse Sherlock's piss.'

A plastic bottle filled with a yellow liquid was waiting for Molly to finish preparing the various tubes on the tray table. Hermione folded her arms and leaned against the wall, watching the pathologist.

'I don't think Molly needs an audience for that,' Hermione said. 'Why did you call me, John?'

'Why didn't you tell us Sherlock was back on drugs?'

'I'm no one' s nanny, John, least of all Sherlock bloody Holmes.'

'How could you not have noticed, you live in the same house!'

Sherlock answered for her. 'No, not any more.'

Mary and John looked at her agape. John moved his head from one to the other, trying to understand what could have happened. Mary and Molly exchanged a glance but said nothing. Hermione tried to look unfazed. 'Mycroft wanted to keep me at Baker Street, I assume to avoid this,' she said, gesturing with her hands. 'But honestly, I'd rather live alone without having to worry about whether I'm going to find a severed finger in my yoghurt. And I'm sure Sherlock appreciates having his room back, don't you, Sherlock?'

It was the first time she had addressed him in almost a month, and she did so, looking at him straight in the eye. Sherlock pursed his lips and didn't respond, which only added to the tension in the room. Right now, it was obvious that something had happened between the two of them. Hermione had hoped that Sherlock's volatile nature would make it easier for people to believe that she had grown tired of his outbursts, as the reality was, as it usually is, far more humiliating. Just remembering it brought Hermione's anger back to the surface.

'Anyway,' Hermione continued. 'I don't know why you've bothered. Look at him. It doesn't take an analysis to know he's off his tits.' Her phone rang again with an incoming message. She pulled it out and glanced at the screen. Mycroft. 'Sorry I can't stay for what I'm sure is an unexpected revelation, but I have more than enough with one Holmes.' Hermione held up the mobile in her hand. 'Next time you want to know Sherlock's comings and goings, John, ask Mrs Hudson. Or call Mycroft. I'm off the case.'

Hermione left the lab without saying goodbye. The words had come out of her mouth unintentionally, as if there was no filter between her head and her tongue. Weeks had passed, and the wound, instead of healing, was still open, exposed like a frayed wire. However, as she followed the river of people heading for the underground, her mind began to wander. Was it her fault that Sherlock had started using again? It couldn't be, she told herself. It had been he who had left and who had made it clear to her in no uncertain terms that he wanted nothing of what she had to offer. Had it been John's absence, the marriage, the change in the status quo?

Hermione buffed and reprimanded herself. No one was at fault for Sherlock's actions. He was a grown man who had decided that the best way of living his life was to dally with death in a wide variety of forms on a daily basis. Whatever happened to him, he had only himself to blame.

And still...

Hermione had had this exact sensation so many times in her life she had lost count. Sirius said it was what made her infallible. The gut feeling that spurred her on, the loose ends her subconscious wove together only to flag her with them, telling her there was something else she was not seeing yet. And that was happening now.

Hermione stopped dead in her tracks in the middle of the street, causing people to bump into her and curse. After a few moments of hesitation, she turned around and walked to the curb to hail a taxi.

Hermione had to wait half an hour, and two cigarettes before Mary's car pulled into the street and parked in front of the house. Mary said nothing but threw her the keys before accompanying the boy home. Hermione went straight to the kitchen and filled the kettle.

'Poor Kate,' Mary said as she entered. On the table, Hermione had left two steaming cups of tea. 'His son will be the death of her.'

'John's on babysitting duty, I suppose,' Hermione said.

Mary hummed over the rim of her mug. 'Are you going to tell me what happened, or am I going to have to torture it out of you?'

'You don't believe me when I say I've had enough of Sherlock?'

'Hermione, dear. You've been working with Mycroft Holmes for years. You have a PhD in Holmes. If John could hold his own in that house, it would be no problem for you.' Hermione sighed and fiddled with the little paper at the end of the teabag. 'So?'

Hermione should have known that no matter how much she kept quiet and tried to make excuses, it was almost impossible to fool a former assassin. Mary seemed to come to the right conclusion with her cup halfway to her mouth and set it down with a thump on the table, causing the hot tea to overflow. 'You've slept with Sherlock.'

'A little,' Hermione muttered and rubbed her face with her hands. Hermione ran her hands through her hair and finally crossed her arms again, dropping back against the backrest. Mary opened and closed her mouth a couple of times, unable to find the words while she wiped the spilt water with some kitchen towels. Hermione decided to tell her the story. 'It was the night of your wedding. I guess we'd been drinking—'

'Not that much,' Mary interrupted her.

'—we got home, one thing led to another, and we ended up in bed. Once.'

'What happened in the morning?' asked Mary. Hermione grimaced. 'Oh, I see.'

'He came back later, and we had a chat.' Hermione was telling the truth, albeit in a sweetened and abridged version. Sherlock had come back, but two days later, interrupting her bath. And talking really wasn't what they had done. Sherlock had done almost all the talking. And Hermione, not knowing how to react to the ball of emotions in her stomach, had chosen the easy way out — the coward's way out. 'I decided it was best to leave Baker Street. I should have known better, really.'

'Then why are you so angry?'

'I'm not,' Hermione rebutted.

'Hermione, this morning you've had nothing but fire coming out of your mouth,' Mary pointed out. 'Besides, I'm the one who should be angry. Since when do you not tell me one of your one-night stands?'

'Mary, it won't be the first time nor the last someone leaves without saying goodbye. Besides, I'm sure you were busy doing the same thing as me, but with someone a bit more dedicated,' said Hermione pointing at the ring on her finger.

'But I sent you a pregnancy test picture!' complained Mary.

'That was unnecessary and pointless,' Hermione dodged a swat from Mary, laughing. Hermione's phone rang again, and Mary saw the incoming call from Mycroft.

'Have you talked to Mycroft?' asked Mary.

Hermione was tapping a message when she answered. 'He hasn't said anything about it, but after today's stunt, I'm sure I will. Somehow this is going to be my fault for not keeping an eye on an almost thirty-something year old adult.' Hermione sent the message and finished her tea. 'Why do you think Sherlock has gone back to drugs?'

'Oh!' Mary leaned across the table. 'He said it was for a case.'

'What case?'

'Dunno. But he said, and I quote, "there's every change that my drug habit might hit the newspapers."' Mary said. 'Any ideas?'

Hermione only responded by shaking her head.

'What are you doing?'

Hermione twisted her head around, balancing on the stool she was on, still with her arms tucked inside the kitchen cupboard over the hobs. Sherlock had appeared in the middle of the kitchen, clean-shaven and showered and clad again in one of his usual suits and coat.

'You need to stop sneaking up on people without warning, you're going to give someone a heart attack one day.' Hermione came down with the coffee pot in her hand. 'Why is everything in different places? It took me twenty minutes to find the coffee. And where's John's chair?'

'Why are you here, Hermione?'

'Investigating,' she replied, and put the coffee pot on the stove. Sherlock laid his scarf and coat on one of the kitchen chairs. 'Mary said something about being undercover. I didn't know drugs were necessary for that. What was it in the end, by the way? Heroin?'

'I am a user, not an addict.'

'Whatever rocks your boat, Sherlock. I'm not interested in how. I want to know why.' Hermione handed him a coffee. As she approached, she caught a whiff of a particular scent, which she had smelled before but couldn't place. She sniffed the air, but Sherlock quickly walked away to his armchair.

'My cases are private,' he said.

'That's why John blogs about them,' Hermione chided. 'If this is an important enough case to jeopardise your health, I'd rather get involved now than have Mycroft force me into it later. I'm just saving myself some work.'

Sherlock nodded and sipped his coffee. Hermione took the opportunity to drag one of the chairs over to where the parsley chair used to be.

'What do you know about Charles Augustus Magnussen?'

Hermione pondered briefly. 'He's a media tycoon; he owns several tabloids, which have hogged the best part of the sensationalist headlines in the past year. A couple of libel suits, rumours of dubiously obtained information. Typical British tabloid.' Sherlock looked at her with an arched eyebrow. 'But you already know that. What else do you know?'

'He's a protégé of the Government. And by Government, I mean my brother.'

Hermione agreed. 'Your brother refers to him as a necessary evil. Sometimes we use him to sway public opinion, or to distract people from something bigger. I personally find those tactics repulsive. He's also quite revolting, for what I've heard.'

'Yes, he is.' Sherlock pressed his fingertips together in front of his face. 'What about Lady Smallwood?'

'Everyone knows Alicia. She has an undisclosed position of priority ultra, much like your brother.' Hermione frowned, remembering something, and Sherlock smirked. 'At the moment, she is leading an enquiry about Magnussen.'

Sherlock stood up and paced towards the window. 'Lady Smallwood hired me to retrieve sensitive information Magnusen has about her husband. After coming from St Barts, Magnussen came here. He seems prepared to make a deal.'

Hermione stared at Sherlock. 'One reason we protect Magnussen is because he never does any substantial harm to anyone of importance. But Lady Smallwood is not a civilian. She could have gone to Mycroft, but she came to you instead.' The information was trying to fit together in his head. 'What does Magnussen hope to gain, anyway? She can't swing the vote alone, and she can't cancel the enquiry.'

'I don't think he wants to win anything, just to show that he can get to her if he wants to.'

'And you think he's just going to give you the information?'

'Give? No.' Sherlock sat back in his armchair, tapping on his phone. 'But there are other ways.' Hermione observed him and gave the room a once-over. She'd noticed when she'd first walked in that the room looked different, and not just because of the disappearance of John's chair. Everything seemed cleaner. There was even a vase of flowers on the table. And there was that peculiar scent that mingled with the smell of Baker Street. Quietly, she got up and made her way to the bathroom, listening to Sherlock get up behind her. Hermione quickened her pace and opened the door. In the cupboard next to the bathtub, besides Sherlock's products, there were two more bottles of shampoo and conditioner, the brand Hermione used. But she was sure she had taken everything with her. She came out of the bathroom and saw Sherlock covering the door to his bedroom. Hastily, Hermione went back into the bathroom and opened the second door. The smell in the room hit her like a kick in the stomach.

Versace.

The same perfume that had clung onto Sherlock's tux jacket on the day of the wedding.

And then she remembered who Janine worked for. How had she not seen it before? Hermione let out a laugh.

'Out,' demanded Sherlock from the doorway.

'That's how you intend to do it,' Hermione said, walking past him into the kitchen.

'I don't know what you're talking about.'

'I work for the MI7, Sherlock, I do background checks on just about everyone I meet. And Janine isn't exactly discreet about her personal life,' Hermione pointed out. Sherlock blushed slightly, and Hermione remembered the bed in the room. Clearly, two people had slept in it, two people had used the shower, and someone with more interest in domestic life than him had rearranged the kitchen. 'Has it been very hard?'

'What?'

'Dating, like a normal person. Faking interest in the comings and goings of little Prince George. Watching Netflix. Does she know you're using her to get to her boss?'

'Who says I'm using her?' bit out Sherlock.

Hermione swallowed. Sherlock had stood on the other side of the table. His hands clenched the back of the chair, and Hermione tried not to think about what had happened on that very table. The conversation she and Sherlock had had two days after he had fled and returned to Baker Street replayed in her head. The detective had made it very clear to her that what had happened between them had been a byproduct of the situation, a mirror image from their best friends' lives. That he hoped she had no illusions that he harboured any feelings for her beyond the physical desire that was now satisfied. That sentiment was weakness, and that she should know by now that it had no place in his life. That Hermione was not part of them. All of this delivered in the ruthless verbal onslaught that was Holmes' trademark.

And Hermione, then, hadn't been able to tell that what was true and what was fear, and she wasn't now either. But it really mattered little. Hermione got the message loud and clear. She walked to the living room and grabbed her coat.

'Just a word of warning, Sherlock,' she said, as she buckled her belt. 'Magnussen is still under Mycroft's protection, and Magnussen himself is a powerful man. Keep that in mind.'

'I'm not afraid of either of them,' said Sherlock obstinately.

'Be my guest. I'm just saying, that crossfire? It's not a place I'd like to be.'

'Are you going to tell Mycroft?'

'What makes you think he doesn't know already?' asked Hermione before going downstairs, vaguely waving in Mrs Hudson's direction. She had completely forgotten to ask Sherlock about why he needed the drugs.

The rain was pouring down hard on the canopy that covered the observation post; the wind making it almost entirely useless. Hermione tried not to shiver as she jotted down the cadets' frankly disappointing lap times in the notebook propped on the table. The cold was bone-shattering.

'This is pointless,' Ali said next to her. The officer had held a pair of binoculars to his eyes, trying to make out the start of the course. It was dark, and despite the lights around the perimeter, it was impossible to see anything.

'You know how it is. Rain, thunder or snow,' Hermione replied. One cadet seemed to be having trouble with the puddles that had formed on the trail. 'Move it, Jackson! It's only mud!' Hermione clicked her pen, incessantly. 'Is it just me, or does no one seem to feel like training today?'

Ali let out a little whistle. 'Someone's in a foul mood.'

'Shut it.' Hermione went back to her notes. Ali tapped the table and pointed to a spot at her back. A jeep was speeding down the dirt road and stopped a few yards from the station. An officer scrambled out of the driver's seat.

'Agent Black, Agent Khan,' he said, squaring himself military-style to both of them, then addressing only her. 'You have a call in the main building, madam.'

'What is it about?'

'I don't know, madam.'

'We've got half an hour to go,' Khan said.

'I'll go straight there as soon as we're done,' Hermione replied, and without taking her eyes off Jackson at the end of the run, she stopped the stopwatch and scribbled down the numbers.

The officer approached her. 'But Madam-'

'Have you forgotten how to obey a direct order from a superior...' Khan peered at the name embroidered on the young soldier's chest. 'Cadet Parker?'

'No, sir,' Parker answered quickly. 'Captain Watson demands to speak with you as soon as possible, madam. He says it's urgent.'

Hermione looked up, her heart pounding hard against her ribs. 'John Watson?' She wanted to make sure, even if it was unnecessary. She didn't know any other Captain Watson. Parker nodded.

'Go, Black,' Khan said. 'I'll wrap it up here.'

Hermione left her notepad behind and stepped out from under the canopy. The rain completely soaked her clothes in the short walk to the passenger door as Parker started the car. The jeep covered the distance to the main building in record time. On the way, Hermione kept gnawing on her lip until the taste of blood flooded her mouth. There was a horrible feeling in her stomach. John never pulled out rank if not necessary, so whatever it was had been important enough for John to dust off his proverbial badge. When they arrived, Hermione practically jumped out of her seat and, with trembling hands, swiped her card through the reader, leaving Parker behind. She jogged down the corridors, looking for the comms room, where a young officer seemed to be getting the telling-off of his life from someone on the other end of the phone.

'This is Agent Black, Cadet Parker told me there was a call for me,' she said, gasping for breath. The officer held out the handset. 'John?'

'For fuck's sake, Hermione. Where the hell are you?' The officer had run out of the room, leaving her alone. John's voice was frantic, but it was cracking. As if he had been crying. 'I've left you a thousand messages on your phone. I had to call Mycroft to know how to contact you.'

'I'm in training camp in the middle of nowhere. What's happened?'

'Sherlock's been shot.'

It took a few seconds for the words to make sense, and Hermione dropped into a chair and tried to take a deep breath. 'How is he?'

'I don't know. They're operating on him now.' John took a breath. 'He came in on cardiac arrest, and when they came out to update me an hour ago, they said he'd flatlined again. I don't know anything else.'

'Where are you? St Barts?' John replied he was, and Hermione stood up. 'I'm leaving now, I'll be there as soon as I can.'

Hermione stormed out of the room and dashed off towards the changing rooms. She pulled out everything she had from her locker, not bothering to take off her wet tactical clothes and change into something dry. After signing the sign-out sheet, she unlocked her car and set off, not towards the main road, but towards a back road that seemed to lead nowhere. Driving back to London would take more than an hour, and the training camp had strong anti-apparition protection wards. The nearest thing outside the perimeter were some old, dilapidated army hangars. Hermione's magic spread through her body as soon as the car drove past the magical exclusion barrier, and she cracked her neck. Hermione picked up her mobile and dialled Mycroft's phone.

'Go on, pick up,' she muttered as she entered the hangar. The call went straight to voicemail. 'Fuck you Mycroft.'

Hermione got out of the car and without thinking, ripped off the number plates, took the identification documents out of the car and stuffed everything into her backpack. She couldn't leave an official car in the middle of nowhere. Hermione took her wand in her hand and hurried to the exit, looking around to see if anyone had followed her. She waited for a few minutes. Then, she cast a Muffliato around the building and aimed her wand at the car.

'Confringo.'

The spell hit the boot, and the entire car blew up, the sound of the explosion bursting in her ears. A group of nearby crows took flight, squawking. Hermione pulled out her mobile phone and searched for pictures of alleyways near the hospital.

She hoped that London's poor street lighting at nightfall would give her an extra layer of protection. Hermione checked the time and decided on a loading and unloading area that should be empty. She pointed her wand at the car again, this time to smother the flames, and closed her eyes.

After the familiar tug under her stomach, Hermione found herself behind a rubbish bin. She pushed it aside, the rain still falling on her. Entering the hospital, Hermione went straight to reception, ignoring the stares at her wet clothes and her smeared mascara. Ignoring the people queuing, she headed directly for the woman behind the counter, which earned her a couple of insults.

'I'm looking for Sherlock Holmes, he's in surgery,' she said undeterred.

'I'm sorry miss, but I can't give you that information. Besides all these people-'

'Hermione!' John's voice echoed through the relatively silent hospital. Hermione raised her head. John was on the first-floor runway and meet her halfway up the stair. Hermione hadn't noticed that she was shaking until John's firm body had embraced her, even though she was soaking wet. Tears began to blur her vision. 'It's alright,' John soothed her. 'They just finished. He pulled through. He's fine, he's going to be fine.'

Hermione nodded as she wiped her cheeks. She sat down next to John on one of the plastic chairs, waiting.

'What happened, John?'

'Where do I begin?' said John. He told her how Sherlock had faked a relationship with Janine, that he'd gone so far as to buy a ring to get into Magnussen's office. That someone had beaten them to it, and that after knocking Janine unconscious, they had shot Sherlock, leaving Magnussen alive and without a scratch.

'You don't think it has anything to do with the documents Sherlock wanted, do you?'

'I don't know. From what Sherlock said, Magnussen has a lot of enemies. It could be anyone.'

'Do you think they'll be able to extract anything from the bullet?'

'We'll see what Greg says.'

Hermione nodded, thinking there was no point in shooting Sherlock and letting Magnussen go free. In Hermione's eyes, a dead Magnussen was much better than a live one.

'You should change your clothes, or I don't know, do...' John said, and gestured with his finger, implying that he could use his wand. 'Something.'

Hermione gave a lopsided grin. 'Because it's not going to look weird if the crazy woman everyone's seen covered in rain and mud turns up clean.' An orderly held out a blue hospital blanket, and she draped it over her shoulders. 'Where's Mary?'

'I called her, but she didn't pick up. I'm sure she's taking a nap. Looks like the end of the first trimester's been rough.'

Hermione closed her eyes and leaned against the wall, trying to find a comfortable position. After a while, John offered her a hot coffee. Hermione pulled out her phone, and dialled Mycroft's number again, with no answer.

'Family of William Holmes?' asked a doctor. John was the first to react and stood up. 'You can come in to see him, just for a few minutes.'

Hermione and John followed the doctor into one of the rooms. On the bed, Sherlock was hooked up to several machines. He had a tube in his nose and several IVs in his arms and neck. And a bandage covered his bullet wound, just below his right pectoral, his skin almost as white as the bandage. Hermione approached the bed. The doctor talked to John, and she thought she heard the words' recovery', 'bed-rest' and 'lucky'. She brushed aside a curl that fell across his forehead and took the hand lying on the bed between her own. Despite the encouraging sounds from the machines, steady and strong, Sherlock was pale and cold, reminding Hermione of how close he had come to dying. So focused was she on him, Hermione didn't hear the doctor leave and only snapped out of her trance when John cleared his throat. Hermione let go of his hand as if it had burned her.

'We can only stay for a few minutes. Sherlock needs all the rest he can get.'

'Sure,' Hermione said.

A groan came out of Sherlock's mouth. Hermione leaned over him at the same time as John left to fetch the doctor. The heart monitor began to speed up.

'Sherlock, shh,' Hermione tried to calm him. Sherlock opened his eyes, muttering.

'Herm...'

'Yes, it's me. I'm here,' Hermione reached for his hand again, but Sherlock tugged at it. With awkward movements, he pointed to where the bullet had entered.

'M...Ma...Mary.' Hermione gave him a quizzical look, but Sherlock didn't waiver. He pointed his finger at the wound again.

Hermione, for the second time on that day, felt all the wind knocked out of her. She squeezed Sherlock's hand, understanding it all. 'Mary.'

Sherlock let go of her hand, and John came in with a nurse who led them out of the room. John sat in one of the chairs in the corridor, a big smile on his face. Hermione, however, felt as if her guts were being twisted. She couldn't face Mary now. But if anyone knew anything more than what they were saying, that was Mycroft. John looked at her.

'Are you alright?'

Hermione smiled briefly at him. 'Yeah, I was thinking that now we've seen Sherlock, and he's fine, I should go and see Mycroft. He won't pick up his phone, I'm sure he'd rather we gave him the news.'

'I'm sure he's had the call from the hospital director by now.'

'He should know from me anyway, he's his brother,' Hermione snapped and tried to calm down. 'Besides, I should get changed. Is it okay if I leave you here?'

'Sure. I'm going to try to get back in touch with Mary.'

Hermione walked out of the hospital, fuming. There were many people who owed her explanations, and Hermione intended to collect them all, come hell or high water.