Gibbs has rules for everything, and the things he doesn't, he's learned to make up rules on the fly, when he needed them. It was an ever growing list, you might say.
Rule Twelve was one of those rules which had evolved over time. It wasn't just there because of the gorgeous female team members he should know better than to flirt with. It wasn't there solely to keep him from losing one of those ex-wives over a one night stand on a stake out in another country.
It was there because something was bound to go wrong. And something always went wrong.
What started with a shared smile and reassuring pat on the back morphed into lunches at her favorite cafe on the slow work days and late dinners of Chinese take out at the office during the tough cases... to burying your heart with her after she died in your arms of a bullet to the brain.
Gibbs hadn't meant to fall in love with Kate. Hell, after three ex-wives, he wasn't intending to fall in love with anyone. He wasn't looking, wasn't in the market, and certainly didn't care if anyone else was looking at him that way. He dated, sure. Little flings with the women Tony called "mystery red head" with a number tacked onto the end or "mystery red head with the hot car" or "mystery red head who buys me coffee, too." Tony liked the three weeks he dated that one, actually.
But Kate hadn't been a nameless red head.
She was a friend with whom Gibbs had grown too closely attached to; a woman who had slowly stolen his heart over the two years he'd known her.
He couldn't be sure just how it had happened, either. While she and Tony antagonized each other like rival siblings, she'd opened up to him, blossoming before his eyes into not only a competnet agent but valued friend. He came to count on her... sitting at her desk, giving him that smile like they were sharing a secret even when they weren't, taking careful note of everything he said. When Kate looked at him, he knew she was listening. He never doubted that she'd taken everything he'd said to heart, no matter what it was. Somewhere along the way, Gibbs became aware of more when he looked at her, not just the desire to be good at her job but the desire to genuinely please him.
Her boss, her friend.
The first confrontation with Ari brought their feelings to the forefront. Well, Gibbs' feelings, at any rate. He'd been denying them, stubbornly sticking with Rule 12 because of what had happened with Jenny, and then Kate's life was thrown into peril at the hands of that sociopath. When it was over, Gibbs became obsessed with finding him again, discovering his name. Hunting him down and torturing him slowly daring to hurt *his* Kate.
Not just a member of his team, but his Kate. The woman he could no longer deny to anyone that he loved.
He loved Caitlin Todd.
He had loved for some time, actually, and it barely seemed like his intentions towards her had been clarified - and reciprocated, blessedly - when Ari intruded on her like a second time. She'd been taken, abducted and spirited away, and while Ari played the suave host, Gibbs had grown more frantic to find his girlfriend. In his heart, in his mind, he could feel the ghosts gathering, Shannon and Kelly ready to welcome another of his loves into the afterlife. He couldn't let that happen, because he and Kate had a shot at happiness, and he would be damned if that monster was going to take it all away.
Gibbs was damned, alright, in the end.
Ari shot Kate, and the ring Gibbs' had bought her just the week before was shoved into the back of his desk, behind a couple of old useless cellphones he'd managed to break and a few medals he'd earned that he'd never gotten around to looking at.
The bull pen reminded him of her. Her desk, which Tony helped to clean out with a reverence Gibbs hadn't known Tony to possess. Her locker, which Abby bedecked with black ribbons and roses for a week before cleaning it out. Her sketch pad, where she had captured the essence of everyone on the team. Somewhere in the back there was one of him. Gibbs didn't want to think about it, or the loving hands which had drawn it in perfect detail.
Nor did he want to think about Ziva taking her spot on the team. She wasn't a replacement. She couldn't replace Kate in that way. Not in his heart.
Nothing, however, especially not his precious rules, could erase the fact that Gibbs had buried another love. Nothing could fill that hole Kate had left behind.
And that, most emphatically, was the real reason for Rule Twelve: to ensure that his place of work didn't become like his home, a mine field of painful memories everywhere he looked.