Anderson really didn’t mean for the thing with Donovan to- happen.
He calls it a thing because neither of them is keen on dating: Donovan is a workaholic and Anderson basically aromantic. Sometimes they watch TV together: That’s as close they come to a date.
It was a particularly stressful day, like those days tend to be, when the cases keep piling up and against their best efforts they just keep running around like headless chickens, scrambling to keep up. And he’d had a row with Lizzie – they were still married at the time – one of the many rows in the past weeks, and it seemed in fact like their life was a huge big row now, split into cold silents mornings at the breakfast table, snide remarks, silent treatment at dinner, sleeping in separate beds, and he was having trouble remembering that he loved her, probably because he didn’t, not anymore.
It was a hard truth to swallow in itself, and the stress had made it no easier, so he’d gone and hid in the evidence room just for a breather, to sit down and rub his face and stare at the bagged, labeled items on the shelves until his head would stop spinning and he could push his failing marriage aside long enough to focus on a triple-homicide.
Donovan had come in to look for him.
Anderson liked her, and perhaps surprisingly for people who didn’t know him very well, genuinenly believed women to be capable of just as much as men: Partly because of the girl who broke his nose in sixth grade and partly because Donovan was a living proof of that. He always reserved a few snide remarks for the blokes who joked about a girl in the force.
She’d told him in no uncertain terms to quit sniffling in the evidence room and he’d told her to stop popping cafeine pills for breakfast and then his mouth had- twisted (Lizzie told him he looked constantly like he was sneering, but this had been worse, he had a sneaking suspicion he’d looked close to crying) and Donovan had changed her tactics completely.
They’d talked for a while, in softer tones as if the seriousness had seeped even into that, about Lizzie and him, and Anderson’s son Mike who was only five and didn’t deserve to hear the hissing whispering of his parents at night, and how he was just tired . It was like talking about death. He didn’t fall in love easily and no one enters a marriage expecting it to end one day.
Somehow they’d ended up kissing, clumsily and heatedly, against a mounted buffalo head, a horn digging into Anderson’s back, Donovan pushing him against it, her hands twisting in the front of his shirt roughly. (He almost suspected she’d just panicked at the idea of someone crying and worked in a distraction.) He’d felt bad, afterwards, of course, but not as much as he’d thought he would. And he’d known there would be no reconsiliation for Lizzie and him.
They continue their thing, even after the divorce, because neither of them sees the reason to stop. It’s just a thing. Sex without particular complications is nice and they work well together, Donovan’s fierce aggressiveness compliment Anderson’s passive snide remarks and even Lestrade seems to take notice of that. He doesn’t feel particularly ready for dating or romance, but casually high fiving Donovan after a solved case works.