The first time it happens, she tells herself it’s a fluke. It’s very different here, and she’s lonely. They start bickering, like old times, and it’s comfortable, like a pair of jeans you’ve washed a hundred times. Before she knows what’s going on, they’re in her bed and McKay’s got that smug, satisfied look he gets when he’s won an argument, even though she’s fairly certain she got the last word in before things went non-verbal. When he leaves, she gathers her blouse, torn in their haste, and she swears to herself it won’t happen again.
Of course, it happens again. This time she’s sure he’s set her up; it’s too formulaic, even for him; he and Sheppard come to her, ready to tear each other limb from limb – God, it’s Daniel and Jack all over again – and once she’s told Sheppard she’ll deal with McKay, he leaves and she does. Twice. She’d never have dealt with Daniel like that; Jack would have killed her. As it is, she’s surprised John doesn’t, except that she’s sure Rodney makes a point of not telling him.
The third time, it’s not as much of a surprise as it was before. She’s expecting it, expecting him to find an excuse to be in her way, a reason to lash out at her verbally. That’s always how it starts. One harsh word leads to another – with more syllables and the implication that she won’t know what he’s talking about and always that pleased sneer when she proves him wrong – and she’s knocking over half the furniture in her office to back him up against the wall, all but tearing his fly open. Then. Oh, then. Then, she gives him something to really be smug about. If she can’t shut him up with her brains, she’s not averse to using her mouth, hands and body toward the same end.
Weeks go by before they find a chance to be alone together. This time, she goes to him. Corners him in the lab, lures him to her room with whispered promises and thinly veiled threats; the things she’s going to do to him when she gets him home would make a sailor on shore leave blush. It’s wrong, she knows that, and not just on a professional level. But she likes things that aren’t good for her; it’s why she lusted after Jack, why she and Pete never worked out, and why she misses her motorcycle, and between that and the fact that he’s really pretty good, it’s more than enough to keep her going back for more.
They fall into a pattern of baiting each other; arguing has always felt like foreplay between them, and they’re both so damn stubborn it seems like they’re tearing each other down verbally, then tearing each other’s clothes off, nearly every day. It’s never tender or slow, but it’s always good.
It isn’t until she looks up from her desk one afternoon – where does all this paperwork even come from, and why did she always want her own command so badly? – to see Sheppard standing in her doorway, looking like he’s torn up inside and watching her that she even begins to realize the others have a clue what’s been going on. He doesn’t tell her to stop, just to be kind when she does. He reminds her that McKay is a civilian under her command, and she reminds him that what his CO does behind closed doors isn’t his business; they both know that’s not true, as long as what she’s doing is Rodney.