A/N: I decided to take a short break from Just One Mistake (or JOM as I call it when no one's watching). I'm on a Harry Potter/Sherlock Holmes crossover kick right now. I wrote "Why Neville Hates Baker Street" because of a previous HP/SH kick, but I wrote it just for me. This one's not a cross over with a story I'm working on already. It's the story I probably should have written instead of the one I actually did.

Neville paused at the door of 221B Baker Street before he pressed the bell. His morning had begun with trying to figure out how best to deliver a magical product to a very muggle section of London. Martha Hudson was an odd type of squibb who preferred to live a completely muggle life, except for occasionally stopping at the Leaky Cauldron just to keep in contact with the magical world. According to Hannah, Mrs. Hudson had once had a fling with Hannah's uncle Tom before she'd gotten married to an American. Hannah had made fast friends with the older woman.

That didn't quiet explain to Neville why he had come to Mrs. Hudson's residence and not, say Hannah, or his Gran, who also knew Martha Hudson. Yet he had been informed that he would be the one to make the gift and to deliver the gift, and get the gift wrapped because it was summer and Hannah was budy with the pub, and Neville was terrible at running the pub.

He didn't think he was as terrible as Hannah made out, but he certainly didn't have his wife's prophetic ability to predict exactly what drink a person wanted before they even walked up to the bar. She told him that it was a muggle trick she'd learned, but she also wasn't sharing it with him, probably because he didn't have the patience for it.

Neville could be incredibly patient for a lot of things, like a stakeout, for example. He could be patient for plants, and for his daughters and wife, and he could even be patient for a potion when he didn't have a greasy git hanging around over his shoulder making him feel inadequate at life. What Neville did not have the patience for was looking at someone in the right way to figure out what they should be drinking.

So he'd made the gift, a balm to help Martha Hudson's aching hip. He bottled the gift and he had it wrapped at a muggle gift store. The fact the only gift store he could find that would wrap an outside gift was one that catered to American tourists so it was very expensive as far as wrapping went and was covered in the Union Jack made Neville wince a bit. If/when it got back to Hannah or Gran, he'd be in for an earful, but he couldn't much help it at this point.

He looked at the brass 221B on the door and sighed. He'd been there for a whole two minutes and no one had answered. He didn't want to be a Weasley and keep pressing the doorbell obnoxiously; he had better sense than that. Yet enough time had passed that he wondered if anyone was home. He reached up and pressed the bell again. He listened, frowning, not actually hearing a bell. Did the bell not work?

Suddenly the door opened and Neville jumped back, not having expected the door to open. An older woman that Neville hoped was Martha Hudson stood at the door. She seemed as surprised to see him as he did to see her. "Oh dear, have you been standing out here long? I'm afraid that Sherlock shot the doorbell a while ago and I've just never gotten it fixed."

"He shot the doorbell," Neville said. As an Auror he'd had training to blend in with muggles, hence is very normal brown muggle suit. (He was a bit dressed more than for a normal day, but Hannah had picked it to deliver the gift and he hadn't argued with her.) Having dealt with muggle law enforcement he knew that citizens weren't supposed to have fire arms. What kind of nut job lived here? Was this why Hannah was so insistent on sending him? Trying to find a safe way to protect her friend? To get the authorities out to her home?

As soon as the thought crossed his mind he knew it was wrong. He'd spent weeks making the balm. If the woman was actually in danger, Hannah would have told him months ago when she'd met the woman (Hannah was good at telling things about people in general, actually. It was a shame she'd become a business owner and not an Auror).

"Yes," Mrs. Hudson said, stepping back to let him in. "You're here to see Sherlock," she said. "Well, come on," she said, glancing at the package in his hand. "That's very nice, but I'm not sure he's going to like it much," she added heading up the stairs.

"Um, actually," Neville started, but ended up following the woman up the stairs. He couldn't actually seem to get his words out or to get her to understand them, so he just gave up and followed her up.

The room at the top of the stairs was exactly the type of mess Neville imagined a flat shared by Ron and Harry would look like if they hadn't gotten married very quickly out of school, and if they'd be muggles sharing a muggle flat in London. He found that comforting. He also found it disconcerting that there was a smiley face painted on the right hand wall with bullet holes in it.

"Sherlock, you've got another one," the woman said, moving about the room and straightening up as if she couldn't help herself.

Neville's eyes moved instantly to the man in the leather chair. He sat around in posh black pants and a white shirt, though also clad in a royal blue silk dressing gown. He was sprawled out on his chair in much the way a petulant child would, except the man was tall, lanky, and old enough to know better. The man's ice blue eyes flicked over to him in a look for bored tolerance and an almost hope until he saw the gift.

"He isn't here to see me," the man said.

"Really?" Mrs. Hudson asked from where she was straightening papers.

"No, Mrs. Hudson, right?" Neville asked, jumping on the opportunity with both feet to be able to do what he'd spent time on the tube for. "My name is Neville Longbottom. I'm Hannah Longbottom's husband, and Augusta Longbottom's grandson. They sent me to apologize for not being able to come themselves and to give you this," he said, offering her the gift. "I'm sorry about the wrapping paper," he added.

The woman looked very surprised and a bit watery eyed as she reached out to take it. "They didn't need to."

"The women in my life inform me that birthdays are very important," Neville said.

"Mrs. Hudson, I didn't know it was your birthday," said a man coming from the kitchen. He was a bit shorter than Neville, and dressed like a normal muggle would: not exactly unfashionable, but more for comfort. He stood with a particularly straight back that reminded Neville of the Aurors who helped to deal with the muggle wars. A soldier then, at some point, or an officer of some form.

"It's just silly," Mrs. Hudson said, sitting down in the chair opposite the overly tall man.

"No, it's not," the soldier said, shooting the tall man a look. Neville caught a look on his face that was almost guilty before it went back to just straight boredom.

"You can tell your wife and grandmother that this was very thoughtful," Mrs. Hudson said. "Should I open it now?" she asked.

"I'm afraid it's not going to be interesting to look at. It's a balm for your hip," he said. Mrs. Hudson looked very pleased, understanding it was magical remedy, one she'd never bother to get for herself and probably very strong since it was a gift. The soldier frowned, not getting why a balm would be a suitable gift.

"No," the posh man, Sherlock if Neville remembered correctly.

"No?" the soldier asked.

"No, John," Sherlock said.

"Sherlock," Mrs. Hudson said in a way that was obviously a chastisement for a crime that had yet to be committed. It was such a mothering tone too that Neville scrapped all the previous notions he'd had of the man being dangerous (to her anyway) and thought of him as very tall mid-thirties adolescent, which he thought was probably more accurate anyway.

"It's not just balm," the man said. "You can wipe that frown off your face. Whatever it is, balm for certain, for pain, also certain, but strong enough and hard enough for Mrs. Hudson to come by that it is a suitable gift," Sherlock said. "Which is odd because Mr. Longbottom here clearly made it."

"How did you know that?" Neville asked, slipping his hands to keep from crossing his arms over his chest defensively. He'd learned a little something able how to present his body from Auror training and growing up.

"Self deprecating but proud. You put real work into it, though you also cut your work down. You don't mention that you made it for one, and comment on how it looks. 'Not much' indeed," the man said, standing up now as he started to swing into his deductions. One glance at the soldier, John, and Mrs. Hudson and Neville could see that he did this often. "You cut down how it looks, the wrapping which you obviously didn't do, paid for by you, though. Only an American gift shop covers a package with that many flags. Yet you also discount the looks of the contents, as if to protect yourself from her disappointment. You're obviously very sure of your abilities, so you're a professional, professional what is the question, but you're good at what you do. You undercut your gift, but don't bother to explain why it's a good gift. If you'd been unsure about your work you would have explained in great detail, but you said nothing about the balm itself other than its base purpose meaning you believe your work can speak for yourself. Back to the profession. You have the fingers of a man who works with plants and soil, dirt under the fingernails which are kept trim for work purposes. You also work with knives, and are habitually clumsy, though you've grown out of it. Your fingers and wrists are scared in many places, most of them facing a few new. This would suggest some kind of botanist, except that you also made the balm which suggests chemist as well. Yet not all the scars match, some are deeper and seem in a more deliberate pattern than a simple accident, probably extending further up your arms, but these are old, adolescent injuries, older school years. Your stance also suggests and officer of some form, though a position you've retired from judging by the way your shoulders have started to lean in again. As a child you had self esteem issues which persist to today, which appear not just in your stance by the way you speak about the gift you've brought, The fact that you've grown past most of these insecurities is obvious by the way you don't talk about the affects of the balm." The man sat back down.

Neville stared at him for a minute, his mind needing a moment to catch up with the very quick speech. "Well, that's not something you see every day," he finally said. It seemed nicer than to tell the man to piss off. Certainly that was what Ron and Harry would have said... Ginny too, probably. Hermione probably would have asked him to repeat everything and hound him to teach her how to do it. Luna would have commented about some nonexistent something that seemed to be able Sherlock's head and ears. That last thought made him relax enough to not just be angry. Imagining the man trying to deal with Luna Scamander was a sweet and silent kind of victory on its own.

"There is one question though," the man said.

"Being?"

"What exactly do you do?"

"Botany, sort of," Neville said, knowing the man wouldn't be happy with just that. "I'm a professor at a private school in Scotland," he said, using the old fallback for muggles. "One of my colleagues is a chemist and I've learned from him… and others. We help each other, mainly," he said.

"Hm… interesting."

"Doesn't seem that way, no offense," John said to Neville.

"It's rather catching, isn't it?" Neville asked, meaning Sherlock's clear disregard for social constructs.

"Sadly," John said.

"Not the job," Sherlock said, interrupting the side conversation. "Mr. Longbottom here is lying, you can tell by the way he looks to the side, but he's not too… fascinating, why lie about this?"

Many reasons, Neville thought. Statute of Secrecy for one. I'd hate to have THAT on my record. Harry gets all kind of hell even still because of the stupid House Elf incident from when he was a kid.

"I'm afraid you'll just have to puzzle over that on your own," Neville said. "Mr…"

"Sherlock Holmes," John said. "I'm John Watson by the way," he added, walking around his chair to shake Neville's hand.

"Neville Longbottom," Neville said. "Got a question for you, what is it that you do?"

"Catching," John said and Neville smiled. "I'm a doctor," he said.

"Really?" Neville asked. "I would have guessed a soldier of some kind."

John looked momentarily unnerved. "How did you know that?"

"Oh, a bit stupid I suppose. It's the way your stand," Neville said, waving it off. "Not as impressive as your friend," he said, glancing at Sherlock who was suddenly deep in thought. "He was right, I used to work with a private investigative agency. Actually, I was trained by a man when I was still in school who taught defensive theory, yeah odd subject," he said with a shy and off handed smile that made him seem self-conscious but harmless and made most people stop asking questions. "He had this saying: "Constant Vigilance". The department really took that up after he died. We got special observance training, had to write down everything we'd done all day and got graded on it. Hardest thing I'd done sense school, but I still remember a few things. Our agency has a few gents who run a couple of investigations in Afghanistan currently. They all pick of that stance after a while."

"Hm," John said, tilting his head to one side, his brows knitting together. "Didn't think that was something you just picked up," he said.

"Mimicry is something else that's important to our agency," Neville said.

"It sounds like Sherlock Holmes institute," John said, shooting his friend a look, who wasn't paying attention. Neville noticed then that Mrs. Hudson had slipped out of the room.

"I can't say I know," Neville said. "But I quit for a reason. I prefer plants to people, even with having to deal with a couple hundred students."

"Teaching's hard?"

"Mostly not seeing my family," Neville said.

"Oh, dull," Sherlock groaned from his seat.

"Ignore him, he gets bored between cases," John said.

"Cases?"

"Sherlock Holmes, the world's only consulting detective," John said.

"Ah, what's a consulting detective?"

"I step in when the police are particularly out of their league which is always," Sherlock said.

"Or when he sees a case that interests him," John said.

"Which entails?"

"The first case I met him on was that set with the serial suicides," John said.

Neville looked confused. "How can you have serial suicides?"

"It was a serial killer," Sherlock said.

"It was all over the papers, did you not read it?"

"No, I'm afraid my family's rather old fashioned, no newspapers or telly or the internet, and the school's the same," Neville said.

"That's… rather… strict," John finally decided on.

"And wrong," Sherlock said.

Both men shot Sherlock a look, but it gave Neville and excuse to look at his watch. "I believe that's my cue to go home," he said. "My wife's going to want me to help her tend bar when I get home, and I can only avoid that duty for so long," he said.

"Right, it was good meeting you," John said, showing Neville to the door.

"Nice meeting you too, John," Neville said and walked out. He'd say goodbye to Mrs. Hudson, get far enough away and the apperate home when no one could see him.

"Sherlock, can you be any less annoying, possibly? He gave Mrs. Hudson a gift for her birthday when we didn't even know and you chased him out."

"Oh please, he didn't come for her. He came because his wife and 'Gran'," he said the word sneeringly. "Told him to be here. He didn't even know Mrs. Hudson."

"Yes, but we do, and we haven't gotten her anything."

"Just delete it, it's not important," Sherlock said.

"Sherlock, it's her birthday."

"Which she prefers to ignore. Don't rush out and buy some cheap trinket just to assuage your guilt at something you had no way of knowing. It won't make anyone feel better," Sherlock said.

"Put your shoes on and get your coat, we're going out," John said.

"What? What for?"

"To go and get a card," John said, sitting down in his chair and pulling on his shoes. "And no, you can't stay here, you're coming too, and we're going to buy a cake on the way home, a good one from the bakery, even if it has to be small, and we're getting her a candle to blow out."

"Human rituals," Sherlock groaned, but he pulled on his shoes, his suit jacket and went for his too big too hot coat (for the summer anyway. If John didn't know better, he'd have thought Sherlock was anemic).

"Yes, and we will be doing a few of them," John said, tossing Sherlock his scarf, which he put on before pulling up his collar.

"It's interesting," Sherlock said.

"What? Human rituals?"

"No. What type of detective agency is involved with investigations overseas in war zones?"

"I don't know," John said, having thought it sounded odd as well. Yet he'd seen some really weird things, especially since he moved in with Sherlock, and Neville Longbottom had seemed rather unassuming and like a good chap and so John hadn't thought about it. Now John was thinking about it.

"Sounds like something Moriarty would deal with, or my brother," Sherlock said.

"You think Neville Longbottom is involved with Moriarty?" John asked, not believing it.

"No, but that doesn't mean he's not involved with Mycroft's business," Sherlock said as they headed down the narrow staircase.

"So, what are you going to do?"

"My brother has always wanted me to get more interested in his business," Sherlock said and John found himself smiling. Sherlock had something to keep his attention and to keep him from shooting more holes in the wall. That really was the best birthday present either of them could give to Mrs. Hudson.

A/N: Okay, so this is shorter than my normal chapters. It was going to be a one shot, but I think I'll make a couple chapters long, and the chapters won't be as long as JOM. Neville is based on my version of him for "The Lestrange Child". That Neville has been in Auror training which I feel was very based on methods that Mad Eye Moody came up with and taught, constant vigilance, as well as a re-jiggered principle of being able to work with muggles and not stand out. So, Neville, while it's not a really happy thing for him, can competently deal with muggles. Next chapter Sherlock gets more curious and Mycroft becomes involved.

Also, how are Sherlock's deductions? That's always hard for me to write.