Right, I've had this on my to do list to post for months. This was originally written for the Sherlolly Smutember challenge over in AO3 and I've just never got round to posting it on here for completeness. The prompt, from memory was public sex or a kink about being watched...I forget. Anyway I hope you enjoy it.

Chapter 1 - The Observer

John was tired and grumpy and generally fed up. He'd been trying to track Sherlock down for almost an hour now and there had been no sign of him. He'd rung and left messages and texts but nothing, nada, zip. They had been working a case together and John had been sent on a errand to interview a witness. He was always suspicious of those kinds of errands. It was normally a sign that Sherlock wanted to get rid of him whilst he worked on the real clues and John would come back with bits of information and theories that would always turn out to be irrelevant or ridiculed.

He'd so far been to Baker St, Scotland Yard and the Diogenes Club and now he was trying Barts. There had been no sign of Sherlock in the labs so now he was trying the morgue. He looked at his watch and rolled his eyes at the fact it was just after eleven. He should be home, in bed with Mary, not on some hunt for a Consulting Arsehole who didn't seem to want to be found.

He decided to take the short cut through the observation corridor which had windows looking down onto the morgue. It would save him having to go all the way down to the basement and back up again if his so called friend wasn't there.

He found the corridor but the light switch didn't seem to be working; it didn't matter, the lights in the morgue were on shedding enough of a glow into the area so he made his way in and looked to see who was down there; finally letting out a sigh of relief when he saw Sherlock in the room below talking to Molly. He had his back to John and he couldn't see Molly's face but it was obviously them. He recognised the purple shirt that Sherlock was wearing and he could see his coat and jacket slung over one of the nearby gurneys.

He was about to leave, to go down and join them, when Sherlock suddenly did something which caught his attention: he put his hand on Molly's cheek, cupping her face. He saw Molly lean into his touch a little, her face visible now. She was smiling and it was such a different smile, one that John couldn't recall ever seeing on Molly's face before; it was a confident smile, a knowing one. Sherlock's touch wasn't a surprise to her, she expected and welcomed it.

John knew he was stood there with a confused look on his face. As far as he was aware Molly and Sherlock were just good friends, nothing more, nothing less but Sherlock wasn't a tactile person; this level of intimacy was out of character for him. It was then that things became even stranger as Sherlock took a step forward and kissed Molly.

John's mouth fell open in shock. This was no chaste kiss on the cheek; he'd seen that before, he might have expected that. No, this was a proper kiss; a lover's kiss. His mind was struggling to make sense of any of this even as he watched Molly's hands slide up Sherlock's back. One hand went to his neck and the other...the other was already pulling Sherlock's shirt up and out of his trousers.

They broke off the kiss for a moment and John found himself instinctively taking a step further back into the shadows so they wouldn't see him if they looked up. He was scrambling for a reason as to why Sherlock would be kissing Molly. Was this some sort of ploy like the time he'd dated Janine?

He knew his hands had formed fists at his side and he swore he would punch his friend if he was messing Molly around. He determined to stay and watch for a bit longer to see how this played out. He knew that Sherlock wouldn't go too far if it was fake.

Signs however were not lending themselves to this being a sham. Sherlock was kissing down Molly's neck and she was leaning back on one of the static stainless steel autopsy tables. Her eyes were closed and she was biting her lips as he moved down. He had obviously undone her blouse and was even now using his mouth on Molly's breasts. John couldn't see anything, didn't really want to (well...maybe he did a bit), but he could see Molly's hands moving in Sherlock's hair and he saw her saying something to him before she pulled him back up for another kiss.

By now he was starting to think that he should move away, go and wait for Sherlock upstairs or better still go home to bed but he felt as though he were rooted to the spot. It was like a puzzle he couldn't quite solve and he didn't want to miss any of the clues, but that wasn't the only thing holding him there.

Molly had just fallen to her knees in front of Sherlock and it became obvious what she was about to do and John's mouth felt dry. His heart beat was thundering in his ears as he watched Molly look up at Sherlock and then he couldn't see her face any longer but from all the body language and movement he knew...he knew absolutely that she was giving Sherlock a blow job and damn it all but watching them was making him hard.

He closed his eyes and swallowed with difficulty and when he opened them again he saw Sherlock's head was flung back, his eyes were closed and his hips were rocking ever so slightly back and forth towards Molly. He still had his back to John but John knew he was enjoying it. The trouble was so was John.

He'd seen plenty of strippers in his time and even indulged in the odd lap dance but he had never paid to see a live sex show and right at this moment he was wondering why because he swore he had never seen anything so arousing in his life. It had nothing to do with the fact that it was Sherlock and Molly but everything to do with it being real and him voyeuristically watching them. This was a kink he hadn't even known he had until right now.

By the time Sherlock stopped Molly and pulled her back up to kiss him John was sporting a rather impressive (at least he was impressed) erection and he was wondering just how fast he could get back to his own home to be with Mary.

He knew he was breathing hard and fast as Sherlock lifted Molly onto the table and pushed her skirt up to her hips. They were both still kissing but Sherlock's hand was between her thighs and John knew the exact moment that his friend penetrated Molly. He saw her eyes open and she pulled away from the kiss as her hand went to Sherlock's face and traced the side of his cheek. Then her eyes fell almost closed as Sherlock started to thrust himself inside her.

John was so tempted to touch himself. An evil voice in his head told him he could have his own satisfaction along with them. He need only take himself in hand and he'd be able to jerk himself off and find his own completion but he fought against that impulse. It was bad enough that he was watching his friends in such a private moment but he'd be damned if he was going to wank over them too.

He couldn't help but press his hand against himself though, adjusting himself every so often and groaning at the thought of how hot sex with Mary would be when he did finally make it home. He pondered whether he'd tell her but he already knew he would. She had a kinky streak in her did Mary Watson and she'd probably find it just as erotic as he did.

Sherlock seemed to be setting a punishing pace and from Molly's expression she was close to an orgasm and it was then that he remembered the intercom. He didn't even really think about the ethics of what he was doing but instead he stepped forward feeling around the edge of the window for the switch which turned it on.

Almost immediately he could hear them, their sighs and moans echoing through the enclosed space. Sherlock was murmuring something to Molly and John strained to make out what he was saying. After a minute or so his hearing acclimatised to the low voices and he could hear his friend telling Molly how much he loved her and how good she felt.

There was a relief in knowing that Sherlock genuinely cared for Molly and this appeared to be a loving relationship but it suddenly made John feel disgusted with himself for invading their privacy in this way. He needed to leave and leave now. So it was ironic that that was the moment that Sherlock and Molly both came, crying out with each saying the other's name.

In the quiet that followed John was nervous that if he made any noise Sherlock would hear him and would know he was there so he kept as still as he could, trying not to even breathe. It was to no avail though as his friend turned his head and looked right at him.

He turned back to Molly. 'See, I told you he'd stay. Did you enjoy the show John? My Molly has long had a desire to have someone watch her during sex so your arrival today was perfect timing.'

John shook his head in disbelief. 'You utter...utter...'

'Careful John there's a lady present...even if she does have a few kinks.' He helped Molly back off the table and they both straightened up their clothing but John was already out of the door. He still had a painfully hard erection to sort out and he could punch Sherlock another time.

It's only a two parter and I'll post the second chapter in a day or so. Let me know what you thought.