Chapter 3 – Occam's Razor

John hadn't stayed long to talk to Lestrade, since he couldn't help him with the ex-prisoner list. Since he didn't know how long Mary would want to spend with Sherlock he left the car for her and grabbed a taxi to take him home, phoning Mycroft on the way to see if he could help. Sure enough he promised to have the list in John's inbox by the time he got home, leaving John to sit back and contemplate Sherlock's behaviour for the rest of the journey. He seemed to be in a better mood when John left to when he arrived, but that didn't completely dispel the unease John felt over Sherlock's reluctance to tell him what had happened Friday night. He knew he wasn't being egotistical to say he was Sherlock's closest and most trusted friend, even if he had waited 2 years to tell him he was still alive after his fall. John had later found out from Molly that he'd only been trying to protect him. Could that be the reason now? But what was he trying to protect him from, and why would he think the best way to do that was from inside a cell? Surely if John and his family were under threat, Sherlock would want to be out there tracking down and eliminating that threat. Unless the threat was that they'd be harmed if Sherlock didn't let himself be arrested, but that sounded far too tame for a master criminal.

No, the threat theory didn't fit, so what else could it be for him not to tell John? Perhaps he felt whatever it was, was a betrayal of John in some way? But how could he possibly have betrayed John, except for putting his family in danger, which John had already decided wasn't an option? Were Sherlock any other man the first thing that would come to mind for a betrayal would be making a move on his wife, but that just didn't sound right either, Sherlock never showed any interest in any woman.

But then Mary wasn't just any woman.

Dismissing the idea as unlikely, John put his theorising to rest as the cab pulled up outside his house, and he paid the driver and got out. He was just unlocking the door when he noticed something unusual.

In the plastic tub outside where they kept the empty bottles waiting for recycling, was the bottle from the Barbito Single Harvest Madeira wine that one of his patients had given him earlier in the week. They had been planning to drink it on Sunday with their roast dinner, but it seemed someone had already beaten him to it. Mary hadn't mentioned having anyone over while he was away, but she never drank alone. Storing the fact away to ask her about later, John continued letting himself in, taking off his coat and shoes and heading for his computer. He couldn't help but glance at the wine rack in the kitchen as he passed the door, and sure enough, there was a bottle of the same wine in the rack. Replacing the wine in apology for drinking it without him, or covering up that it had been drank? He let himself be pulled into the kitchen, opening up the dishwasher. It had been put on last night and was waiting to be emptied, but there was no wine glasses inside. He moved on to the cupboard and sure enough all the glasses were in there, but the front two were noticeably dull and streaky compared to the others; the way they went when John had once hand washed them for fear they'd break in the dishwasher, only to put them in the dishwasher afterwards anyway because they were still so dirty looking. Why would Mary hand wash the glasses when she was going to put the dishwasher on? Unless she was tidying them away in a hurry to hide them.

Suddenly his theory about Sherlock's behaviour being to do with his wife seemed slightly less unlikely.

Heart hammering, John followed his deductions to the bedroom, beginning to hope he was wrong. Opening his bedroom door felt like being back in Afghanistan, about to sweep an unknown room for hostiles. The door swung back to reveal a perfectly unthreatening and tidy room. But it was too tidy. The bed sheets had been changed 2 days early and moving further into the room he saw that the bin had been emptied earlier than usual as well. That left only one place left to check; the wheelie bin.

Usually he would baulk at digging through someone else's rubbish on a case with Sherlock, but this was his rubbish and he simply had to know. In the end he didn't even have to dig through; the contents of the bin had just been tipped in on top of the other bin bags, and there, quite clearly at the top was a used condom and wrapper.

A wave of nausea threatened to overcome John, as reality crashed down on him. Yes it was possible that some teenagers had used their bin after a drunken public quickie, but that didn't happen much round this area. And then there was the condom packet; the same brand that he and Mary had been using before she got the implant, some of which he knew were still hanging about in the house.

As much as he'd like to disbelieve it, all the evidence pointed to the fact Mary, his wife and mother of his daughter, had cheated on him. The question was, was it with Sherlock, or had Sherlock simply discovered her with someone else Friday night and been threatened into silence? Goodness knows she was capable of that.

John slowly unclenched his fists, pushing the surging anger back to focus. His control over his emotions would never rival Sherlock's, but Afghanistan had taught him some. Do what needed to be done first, then deal with the emotions after. Repeating this to himself like a mantra he headed back into the house, left a note for Mary simply saying he had gone out, and came back with a latex glove from his medical kit and nappy bag. He carefully plucked the condom from the bin, bagged it and binned the glove, before taking off down the road to the main road where he could flag a taxi to Barts, hoping that Molly was in today.

Thankfully she was, and he even managed to catch her between autopsies.

"Oh, hello John," she said brightly as ever "No Sherlock today?"

"Um no, he's... Unavailable right now." John skirted.

"What can I do for you today then? If it's about the ears, I'm sorry you wasted a trip but I already told Sherlock no." Molly chatted away, bustling around the morgue cleaning up from her last 'patient'.

"Um no, it's not ears it's um…" He held up the bag with the condom in it. "DNA testing."

To Molly's credit, she didn't bat an eyelid at the contents of the bag. "How old?" She asked.

"Between 24 to 48 hours." John guessed, trying to be as clinical as she.

"Oh, probably still some live ones then, should make it easier." Molly said cheerfully, snapping on some gloves. "Is it just the male you wanted to identify?"

"Both, if possible."

"Well no guarantees, but I'll see what I can do. It'll take a little while, I don't know if you wanted to hang around or…"

"No thanks I'll… give me a call when the results are in yeah?" John said awkwardly. Now there was nothing more he could do but wait, it was getting harder to keep his emotions at bay, and was rapidly feeling the need for some fresh air.

"Okay well… tell Sherlock I said hi. He hasn't popped in in a while and… well it'd be nice to see him"

"Okay, I will." John quickly assured her, straining not to run from the room in his haste. He walked the halls with military stiffness until he made it outside the hospital, leaning against the wall and taking a few big breaths for composure.

There was no denying it really, no use clinging to the small hope that it had all been coincidence and that Mary hadn't really been unfaithful to him. No, if running around with Sherlock had taught him anything it was to never ignore a coincidence, as they were rare indeed.

And it wouldn't be the first time Mary had lied to him. Had hurt him. Had betrayed him. He felt it as sorely as when he'd found out she'd shot Sherlock; the anger burning in his stomach at the same time as a coldness seizing his heart, making him numb and hyperaware of the situation at the same time.

The question was, had his friend betrayed him too? Had both people he trusted and loved most in the world turned on him together?

In a way, the thought didn't feel so bad. It should. He knew he should want to kill Sherlock if it were the case, and part of him did. But the other part of him… would be relieved. And not only because it would save him from his current predicament, but because the idea of him with Mary was somehow preferable to her with someone else.

Because he had seen the spark between them, hadn't he? Even commented on it, albeit sarcastically as they sat around at Baker Street, calmly discussing how she had shot him then saved him. He had been secretly glad the night Sherlock had come back and Mary had smiled and said 'I like him', and when she had excitedly read the blogs of their time together. After all the girlfriends he'd had who had left because they couldn't tolerate his closeness to Sherlock Holmes, he had been greatly relieved that the one he intended to spend the rest of his life with had not only accepted, but encouraged their friendship. And Sherlock for once had not a bad thing to say about her either. It had seemed perfect.

So if they had given into their mutual interest in one another, at least he knew it was that. At least he knew that the person bedding his wife truly cared about her. Because wasn't that better than the alternative? Someone who could care less about her other than as a warm body at night? And what would that say about him, if she was resorting to sleeping with the postman? He liked to think he could keep his wife satisfied, but if it was some random bloke she'd slept with, what else could it be than that he wasn't? Or the only other option, if it was some long forgotten lover shown up from her past life? She might be considering running away to be with him, but if it was Sherlock, then that wouldn't be an issue, would it?

And that's when it clicked. The same thing that it had taken him months to realize the first time round, but when it did, made his decision so much easier. The fact that he was far more afraid of losing her, or rather them, than he was angry at them. And the fact that they would go to such lengths to keep it from him suggested that they felt the same. Oh that didn't mean that he wasn't still angry, but there was a light at the end of the tunnel. He could be mad at them, but he wouldn't have to lose them, and that was a far more unbearable thought than what they had done was.

It all came down to what Molly found. He was almost tempted to go back in and wait in the lab like she'd first suggested, but as it happened, he didn't need to. His phone rang in his pocket and it took him only a few seconds to pull it out and answer, despite almost fumbling with it in his haste.

"Did you get them?" He asked nearly breathlessly, for once not bothering with social niceties as he often scolded Sherlock for, in his desperation to know.

"Um... Hi John. Yeah, I… I got them. Your man it was… it was Sherlock." She said in a small voice, the one John had heard many a time after Sherlock had insulted her. John could almost sympathise with her disappointment, was it not for the wave of emotions that accompanied her news. Despite his previous thoughts that it would be better if it was Sherlock, he was still very angry, and had to take a deep breath to calm himself, almost missing her next words.

"I couldn't identify the woman; there were some cells there, but I couldn't find a match for her DNA on our records."

He wasn't surprised, not with her past. The fact that the records were missing was all the proof he needed.

"Mary… it was Mary." He breathed, not sure why he was telling Molly, but somehow needing to.

"Oh, John. Sherlock didn't send you did he?" Molly replied, all self-pity gone for her voice replaced with genuine empathy.

"No. I just… needed to know." John admitted.

"Of course. Listen if there's anything you need… I mean other than the use of my lab, if you needed to talk to anyone… ever. Not that I'm trying to replace Mary, I just-"

"I know." John assured her. "Thank you. Actually there is one thing you could do for me."

"Anything." Molly prompted him.

John smiled sadly. "Don't give up on Sherlock. I don't know whether this means he's ready for a woman in his life, but if it does I think it should be you, not Mary. Hopefully it won't take him too long to realise that either."

"Are you asking me to distract Sherlock from your wife?" Molly tried to joke, hoping it wasn't too soon. Thankfully John laughed.

"Oh don't you worry, when I'm through with him, he won't need distracting to keep his hands off my wife."

He pulled the phone away from his ear to hang up, but Molly's voice called him back.

"John? Don't you give up on Sherlock either."

"I haven't" John assured her, hanging up the phone and hailing a cab, sending a text to Mary as he climbed in.

Sherlock's cell, 20 minutes. J x

"John!" Mary called across the foyer of Scotland Yard, arriving minutes after him as he waited for Lestrade to come down. "What's going on, did you find something?"

"You could say that." He replied, trying to keep his voice level though unable to look her in the eye. Thankfully Lestrade's arrival distracted her from thinking anything of it.

"Well that was quick, you only left just over an hour ago." He said with a hopeful grin, "You'll be wanting to talk to Sherlock, I take it?" He added, grabbing a pair of keys from the desk Sergeant.

"Both of you actually." John clarified, following with Mary to Sherlock's cell. The air was tense with mixed emotions as Lestrade unlocked it, Lestrade hopeful, Mary wary and John determined.

"John? Mary. Well that was quick, news on the case already?" Sherlock asked, watching the three of them file in, an obvious prelude to some either very good or very bad news. John's tense stance said bad, but not so bad that Sherlock could see what was coming.

"Not the case exactly. Your alibi." John said in measured, steady tones. He shifted his weight slightly, only a small give to his emotional state, as Mary behind him paled, and Sherlock resisted the urge to flinch. Only Lestrade seemed apparently unaffected by the sudden mercurial shift in the room's atmosphere. "I'm going to give you one more chance, Sherlock." John continued, his tone getting sharper. "One more chance to tell us – to tell me where you were on Friday night."

Sherlock's eyes flicked to Mary, for her permission. She gave the smallest of nods, and he turned back to John, keeping his eyes on his friend as he spoke for the record to Lestrade.

"On the night of Friday 21st September 2014, I William Sherlock Scott Holmes was at the Watson's residence. Engaging in coitus with Mrs Mary Elizabeth Watson."

Lestrade's jaw dropped. Whatever he had been expecting Sherlock to have been hiding, it hadn't been that. A million questions buzzed round his head, and he had to remind himself that he wasn't here for juicy gossip, but to do his job. Clearing his throat he turned to Mary, "Right then… Mary do you confirm Sherlock's location at that time?" He asked, as professional as possible.

"Yes." She gasped, tears streaming down her face as she stared guiltily at her husband, as though waiting for him to pass sentence on her.

"Right then I'll… I'll go… get things sorted then." Lestrade excused himself awkwardly, leaving the three to do some seriously needed talking.

"John, I-" Mary started as soon as they were alone, but John held up a hand, instantly silencing her. He finally released Sherlock from his accusing glare, dropping his eyes to the floor and taking a big breath before lifting them back to Mary, forcing words he had prepared in the taxi over out of his lips.

"Mary. Am I in any way not adequate, or not fulfilling your needs emotional and sexual needs, as a husband?"

"No!" Mary vehemently answered, her hands fluttering in need to touch him but not certain they would be welcomed. "No of course not, you couldn't be more perfect. I love you, I just… please, you have to understand this isn't about you it's -"

"Him." John finished for her, with a firm nod, turning back to Sherlock, who hadn't moved an inch since his confession. "You do realise I'm going to have to hurt you for this, don't you, Sherlock?"

"I know an alley in Peckham with no CCTV and neighbours who will turn a blind eye to any kind of violence." Sherlock answered immediately, seeming more welcoming of John's anger than he had his help earlier in the day. "Though I would prefer it if we waited until after the current cased is solved, as chasing a criminal with broken ribs might be problematic."

John couldn't help the laugh that escaped him, his anger somewhat disarmed by Sherlock's answer. He shook his head, trying to clear it as he looked back and forth between his wife and his best friend.

"Okay... okay." He sighed. "I just… I'm still very mad at you both, and if anything like this ever happens again-"

"It won't." Sherlock and Mary answered simultaneously and earnestly.

"I should think not, but… if it does I don't know if I'll be as able to forgive either of you, but as it stands… I'm already halfway there so… yeah, just don't pull anything like this again. And y'know, some grovelling in the form of housework and gifts wouldn't go amiss either."

"Dibs on the jumper." Sherlock shot at Mary as he stood from his bench, referring to a jumper he'd seen John admiring and pointed out to her as a potential Christmas present.

"Already in the wardrobe. Bought it yesterday" Mary replied with a smirk.

"Great way to tip him off that something's up" Sherlock rolled his eyes.

"Actually I didn't get that far, the empty bottle of wine and changed sheets were far more suspect." John said, unable to prevent himself in gloating slightly at his detective skills.

"Well done, John, you've obviously learned more than you usually let on." Sherlock backhandedly commended him. "But you'd need more evidence than that before you'd believe it. I suppose I should be expecting another slap from a certain pathologist next time I need to visit the morgue."

"I'd recommend accepting her invitation to coffee next time." John suggested with mock innocence.

A timid knock on the door interrupted their banter, and Lestrade warily stuck his head in, clearly expecting to be interrupting far worse.

"Um, just letting you know everything's squared our end if… things are cool here?"

"Right, I'd better get the Mrs home then. Have fun figuring the rest out Sherlock, I'll see you in Peckham about 7?" John said with exaggerated casualness, enjoying the confusion on Greg's face. Sherlock smirked in return, waving them off as he turned back to Lestrade.

"All good here Detective, now where are those case files? Can't be sitting around in a cell all day when there's a case to solve!"

AN: I Know, ridiculously cheesy ending. It was that or trail off pathetically.

So thats all folks, thanks for reading and for the follows and favorites and reviews, I really wasn't sure if anyone would be interested in this, so I am glad some people liked it. And apologies to those who didn't/were hoping it was something else going on, as previously stated, I know the concept was out of character, but the the plot bunnies were just eating away at me.

Again thanks for reading :)