A/N: Oookaaayyy, tell you something... I know I'm going to go straight to hell for that one.

Actually, I planned to use this idea only as a fragment of a bigger story... but then it got a life of its own and recieved more and more details. And before people come screaming at me: I'm not convinced that this is really in character, although there definitively is some darker edge to Jack and probably also to Ianto (well, okay, I know there is, as he obviously lied about almost everything concerning his family/past, which I deem as something dark as well).

WARNING: This is pretty dark and might be slightly disturbing to sensitive people.

A Glimpse of Darkness

Whatever exactly the relationship between Jack and Gwen was, it could be definitively highly unhealty and with more than just a tendency to be destructive at times; at least as long as there was no possibility to vent off and escape that unbearable amount of unresolved tension between them. There was no question that Jack wanted Gwen – he sometimes even moaned her name when they were together in bed and that were probably the most humiliating moments of his life – Ianto had just never been sure how much, or he had hoped it was just a fantasy, until… well… he literally got a glimpse of darkness; yet another one.

Jack and Gwen had already been close, very, very close to what could've have been considered a full-blown destructive and probably devastating meltdown, and he had witnessed it with a front row seat – accidentally, although he knew very well that there were no accidents at Torchwood. It hadn't been in any way coincidental that exactly this CCTV was playing on screen in Jacks office as he waited there for him to show up (Jack had told him to wait there), or that Jack forgot to switch off the comms. Ianto later on figured out that it was just another one of Jacks trials in persuasion of having Gwen join them, until it almost backfired.

***

"God… it's been a long day." Gwen, already dressed to leave, her small bag slung over her shoulder, sighed. "See you tomorrow then." She waves her hand at Jack, smiling, innocent and careless and strides in direction of the exit.

"Gwen." As Jack had probably planned his voice made her stop and turn to face him again. It had been as much a plea as a demand; of course he wasn't asking, he was Jack Harkness and he always got what he wanted, so why ask in the first place? "You could always stay for the night." And he's not suggesting that they'd have some actual sleep, not even for a second.

Even without really seeing it – the resolution of the CCTV image was too low – Ianto knew that Gwen rolled her eyes at him. So far this had been nothing he hadn't seen before; it actually wasn't the first time Jack had almost openly said what he wanted: her. After the deaths of Tosh and Owen being subtle hadn't been on his agenda anymore.

But then Gwen makes an unanticipated move, probably surprising all three of them, because instead of just shrugging, shaking her head and leaving without another glance, as she normally did, she walks back towards Jack and tiptoes a little to place a chaste kiss on his lips. "Sorry, that's not going to happen." She mumbles and it sounds more anguished than actually apologetic; they both wanted this, that much had been obvious from the start, but Gwen had chosen to marry Rhys and she was obviously determined to stick to that decision. Jack had therefore already changed his approach to the issue, because no one was able to resist him indefinitely. Since brute force didn't seem to work, he now chose to wear those defences of her down, like the sea that would wash a mountain away given enough time; that strategy seemed to be more promising but also obviously led to more sexual frustration on Jacks part. And a frustrated Jack was even more of a bastard than a satisfied Jack, and sometimes, in his own dark moments Ianto wished that Gwen would just give in and let Jack fuck her.

Jacks hand on her shoulder stops her once more as she had already turned again to walk away. "How long will you keep on walking away from me like that?" The voice is low and husky and as Ianto noticed also a little bit angry, frustrated.

Gwen's taking a deep breath, closing her eyes shortly, exhaling deeply. "As long as it takes." It's almost ridiculous with how much determination Gwen is apparently willing to suffer, to deny what she desires.

"What if I order you to stay?"

There's no hesitation, not for one second. "You won't." Ianto doesn't share Gwens obvious determination when it comes to that matter. Jack had chosen from the start to share his darker moments mainly with Gwen (and he was jealous about it if he was honest to himself, but honesty wasn't a luxury he indulged in very often), but Ianto had enough imagination left to realise that it was only a matter of time until Jack would maybe indeed order her to stay for the night.

"And what makes you so sure about that?" The dark edge in Jacks voice must have even made it through to Gwen by then, as her next answer sounds a little less sure, but still almost sickeningly sweet and innocent.

"Because you're a good man."

That's the moment where Ianto held his breath, almost shuddering in anticipation, almost aroused – at the same time feeling disgusted with himself.

The answer clearly sends Jack off, bringing his angry and frustrated, his dark side to the surface. He grabs Gwen roughly and practically shoves her against the nearest wall, pinning her body against it with his own, her back pressed tightly against his front, one of his hands cupping a breast and surely squeezing (because Ianto knew Jack had been gagging to cop a feel), while the other one tangles in her hair, pulling her head to the side, forcing her to face him. "That's where you're wrong." Jack hisses, his lips brushing hers with every word, their faces only millimetres apart and Ianto can see Gwen quiver, just a bit. The sexual tension is almost palpable. "I've never been a good man and I never will be. I'm a bastard that always gets what he wants because he simply takes it."

"And now what? You're going to rape me?" Ianto is amazed, no almost a little taken aback by the balls Gwen obviously has, as she stares right back into Jacks surely lust clouded eyes, unabashed, the only thing giving her away the slightly shallow breathing he hears over the comm.

Jack's pressing himself a little harder against her in response, leaning in, just this little bit closer that would allow her to feel the full extend of his desire and Gwen trembles almost violently in his grasp. His lips are at her ear, so excruciatingly close, his hot breath tingling on her skin while the hand that had been pulling at her hair runs roughly over her body, feeling all those delicate curves through her clothes. "Don't think that thought never crossed my mind." It's only a whisper, but full of darkness, full of lust and Gwen gasps, a sound somewhere between fear and surprise, as he rocks his hips against her, just a little, his erection pressed firmly against her. It's there, raw desire, primal need, scorching lust, emotions so dark and dangerous and fierce that Jack normally keeps them locked up deep inside himself, buried, and now everything is surfacing, threatening to swallow Gwen; precious, naive Gwen, always so unsuspecting and blindly trusting, almost innocent.

Ianto imagined he could almost taste the adrenaline that must have been running through Gwen on his tongue. He heard the breath hitch in her throat and imagined to hear her pulse, a rapid, fluttery staccato, drumming in his head. That's what fear feels like, although it could also be mixed with a little bit of excitement and Ianto knows that Jack knows, knew and relished the moment, his lips at Gwens neck, while she seemed to be paralysed in his grasp, his tongue caressing her skin, tasting the slightly salty sweetness that's uniquely her, knowing that he is watching, getting almost equally aroused by the situation.

And then Jack suddenly lets go of her and takes a step back, composing himself, obviously forcing, literally willing the thoughts of Gwen and what he's desiring to do with her out of his head and Ianto lets out the breath he'd been holding, feeling ashamed of the erection straining against his pants.

Jack's panting from the effort of letting her go, the effort of pushing back the darkness that had been only waiting at the edges of his consciousness to take over the second he gave in to the temptation.

Gwen swallows hard, twice, takes a deep breath, closes her eyes just for a second, and forces herself back to her normal composure. When she then turns to face Jack, it's as if nothing had ever happened, as if there wasn't the still very obvious bulge in her boss's pants and if he hadn't shared his dark fantasies with her only seconds ago, his breathing ragged, his eyes heavy-lidded with desire, boring into her.

She simply glares at him; steady, calm and obviously totally unafraid. "See you tomorrow then." If it hadn't been for the slightly helpless gesture with which she brushed some dust from her leather jacket and jeans before she turns to walk away, Ianto had almost thought that what just happened left her cold. On another CCTV camera he sees her leaning against the wall, out of Jacks sight, eyes closed, one of her hands running over her face and the sudden display of desperation and defencelessness is painful to watch. But then she straightens and leaves, back straight, her stride almost carefree again and the Hub door finally closes behind her, the sirens stop blaring; Jacks fist was hitting the concrete of the wall hard enough that the skin of his knuckles tears upon the impact.

***

He had been just a very obvious replacement fuck that night, and it took hours for Jacks anger and dissatisfaction to completely wear off; Gwen had him really riled up.

And in the end Ianto was never sure what about that incident left him feeling so very much uneasy, almost sick down to the pits of his stomach. If it was the easiness, the devil-may-care-attitude with which Jack had blurted out his dark fantasies or rather imposed them on Gwen, the way he had been turned on by watching Jack half-threatening or already being close to violate his colleague or the serenity with which Gwen had almost casually shrugged it all off.

They all had gotten a glimpse of total darkness that night and it still somehow scared the shit out of him, although both Jack and Gwen were acting as if it never happened.

Officially it never happened anyway.