Title: Inevitable
Rating: NC-17
Spoilers: Both Gibbs' and Abby's relationship threads throughout season four.
Summary: We shouldn't, and we both know it.

Author's Note: I had this little three-paragraph smut scene in my random scene-snippet document. For some reason it all of a sudden screamed 'infidelity-fic!' at me, and this is the result…

"You got termites again?" Abby looks at me incredulously over her Caf-Pow!. "They only fumigated your house about six months ago."

I shrug, taking a sip of my first coffee of the day and feeling the near-scalding liquid trace a path down into my stomach. "I know."

"It's the boat. It's gotta be. Not only is your house made of wood, but you have too much wood inside the place." As if her theory's completely logical, she sets down her cup and turns to cancel an AFIS search that's come up with nothing. "So are you staying at Lieutenant Colonel Mann's house tonight?"

Though her words are perfectly casual and genial, there's always an almost imperceptible edge to Abby's tone when she mentions Hollis. I know it's there, but I choose not to analyse it. The same way I don't think about exactly why I choose not to. "She's out of town this week."

"I have a spare bed if you want it."

I've been to her apartment countless times, and unless she's ordered new furniture I can't see how this is the case. "You only have one bed, Abbs."

"Which will be going spare if I sleep in my coffin," she points out, and I can't help but smile. I'd planned to go to a hotel for the night, but Abby's always good company, and I once heard her tell DiNozzo that she finds the coffin just as comfortable as her bed.

"Don't you move around in your sleep?" Tony wanted to know.

"She doesn't," McGee had confirmed from across the room. "And one time her breathing was so quiet, I actually thought for a minute that she was dead."

"So he woke me up. And then-" Seeing the mischievous glint in her eyes, I'd chosen that moment to interrupt their conversation. Hearing about her private relationship with McGee has always been low on my list of priorities. Again, this is something I choose not to scrutinise too closely.

"As long as you don't have plans," I tell her now, and her eyes light up.

"Cool! Do I get to braid your hair and paint your toenails?"

Shaking my head good-naturedly, I leave the lab. "I need that DNA match by noon, Abby," I call back to her, hitting the button to call the elevator.

The day passes quickly, and before I know it Abby's stepping back to let me enter her apartment. The place is decorated pretty much as I'd expected before I saw it for the first time. Her landlord refused to let her paint the walls, but her drapes, rugs, couches, bedding and cushions are all dark hues, from black to purple to navy blue to deep maroon. Though the rooms look as if they came from a nineteenth century vampire novel, Abby is forever hyperactive and cheerful.

The first thing I notice on this particular visit is the vase of flowers sitting on the small table just inside the door. On more than one occasion lately, bouquets have been delivered to the Navy Yard for her. When it happens, she reads the accompanying cards with a small, secretive smile before getting back to work.

Though she has no qualms about sharing details about lovers she had weeks, months and years in the past, for the most part she doesn't mention current relationships until they become retrospective. The only thing I know about the guy she's seeing at the moment is that he treats her well, and I don't pry. Don't ask, don't tell is something I carried over from my days in the corps.

Abby hands me a beer before I've even taken off my jacket. When we first met, I assumed she'd favour wine and cocktails, but she's since proven that she can – and does – drink anything, beer included.

We eat takeout and Abby channel-hops, finally settling on a detective movie that's just started. She's seen it before – I haven't, but within ten minutes I've put together a theory as to who the murderer is.

She stares at me with such astonishment that I know I'm right. "You've totally seen this before." I shake my head, and she asks, "How…?"

"My gut," I tell her, and she rolls her eyes in amusement, beginning to search through the channels once more.

Neither of us is really paying much attention to the TV, however. We never seem to run out of things to talk about, and the conversation continues well into the night, until we're both a little inebriated and decide to switch to coffee.

"New theory," Abby says, placing the coffee mugs on the table and sitting back down next to me. "The termites knew you hadn't had any actual fun in a while, so they decided to infest your house so that you'd get out of your basement."

I eye her tolerantly. "Termites that think?"

"Oh, you mock, Gibbs, but have you ever been a termite? No one can possibly say for sure that they don't plot and scheme."

"I get out of my basement more than you think," I tell her, thinking of Hollis for a brief moment.

She leans forward, her eyes curious. "But do you have fun?"

As always, her words are innocent, containing no hidden implications. But for some reason my first thought is that her query's a challenge, calling into question whether the time I spend with Hollis might be better spent with Abby. And though I dismiss the thought as soon as it flits through my mind, it's replaced with other ideas, other images that overtake my common sense.

I run my fingers lightly over one side of her jaw, and she tilts her head into my hand, her expression showing the same conflicted emotions that are flowing through my consciousness. I'm with someone – she's with someone – but she's Abby, and in some unacknowledged corner of my brain I've wanted her for a long time. Her skin is soft under my fingers, and as I stroke her cheekbone with my thumb I catch a glimpse of intense desire in her that snaps the slender thread of my self-control.

I press my lips to hers, and with a tiny gasp of release she returns the kiss. It starts soft and slow; when her tongue teases mine for a brief moment before withdrawing, I deepen the embrace until she draws back, gasping.

About now, the guilt should be setting in, but my mind is blank of everything except the here and now. I want her, and I can feel her pulse jumping rapidly under her skin. She breathes my name, and I can't help myself.

Our lips connect again, and the electric undercurrent between us, usually so steady, surges. I pull her body against me, and she takes the cue to climb into my lap, straddling my waist, beginning to grind against me. The sensation is breathtaking, and I know that if I let her continue we'll soon be past the point of no return. With the last of my failing restraintI grab her hips to halt her movements, trying in vain to control the impulse to drag her into another kiss.

We shouldn't, and we both know it. For a few seconds more I manage to hold out, trying to remember the logical reason that I shouldn't let Abby get her own way, but when she leans forward, seeking my lips again, I can't resist any longer. My arms go around her as I kiss her hard, and she gives a tiny cry of relief, her hands tugging at the hem of my shirt.

Her enthusiasm is contagious. With urgent fingers, we strip away the clothing that separates us, barely pausing to breathe. My mouth closes over a hard nipple and she arches her back like a cat, pushing herself closer. Her fingernails scratch over my shoulders as she takes me into her, her forehead pressed against mine. She surges against me, driving us further out of control until she digs her fingers into my arms, her entire body going taut as she gasps out my name. The feel of her contracting around me sends me over the edge, and I spend myself in a white-hot swell of pleasure.

Gradually, my senses return, and I register the weight of Abby collapsed atop me, her fingers idly tracing a path across my chest. Her breathing calms as the minutes pass, and my conscience at last begins to speak to me. I don't make a habit of cheating on my partners, and from the way Abby's fingers suddenly halt their movement, she doesn't either.

"Oh, god," she whispers.

I'm right there with her.

She doesn't try to distance herself from me, and I don't try to push her away. I should, but I don't.

"I'm seeing someone." The words are quiet, hollow.

"I know." Admitting it makes it more real. I don't bother to point out that I'm in a relationship as well; she already knows that.

"I know it's like the worst excuse ever, but if it'd been anyone other than you I wouldn't have done it." The words resonate deep within me; they could have come from my own lips.

I tilt her chin so that she'll look at me. Her face is guilt-stricken, but when our eyes meet her expression softens, and I can tell where her thoughts are heading.

"No!" The word is for her own benefit, a command to herself, and she struggles upright, reaching for her clothes. We dress in silence, not trusting ourselves to look at each other or speak until we're fully clothed.

She crosses the room to the other couch, and curls up on it, watching me. "Talk to me, Gibbs."

Part of me abhors myself for letting her take things as far as this, but in the back of my mind I know it was only a matter of time. If not tonight, it would have been some other night, some other situation. We've been working up to this from the first time I took her to dinner, years ago.

Abby is a magnetic force that draws me to her, and I know that now we've surrendered to this once, it'll keep happening, no matter how much we try to resist. There are only two choices – avoiding her, and so avoiding temptation, or giving in to the inevitable.

"How do you feel about the guy you're with?" It almost kills me to ask.

She whispers, "He's sweet, and thoughtful, and smart… but he doesn't drive me crazy the way you do." She hesitates, and then asks, "And you?"

I think of Hollis – her dry sense of humour, her hunger for commitment, her sensual charm. I care for her, but comparing her to Abby is like trying to compare a tiny, frozen ice cube to the vast, tempestuous ocean.

I cross the distance between us and pull Abby off the couch, into my arms. She clings to me, murmuring, "It's always been you, Gibbs."

I search her face, and the last traces of foggy uncertainty clear from my mind as I find the same clarity on her features. She's always been my girl, and that's all I need to know.