Set during Season Two.
It ends with a whimper—specifically, his, though he manages not to let it out until he has put a few doors between them.
"It" started with one of his late afternoon visits to Abby's lab. His latest case report was almost in order and he had gone down to get a copy of the fiber analysis Abby had been working on. McGee wasn't typically a very active guy. He did his time on the treadmill to keep his legs and lungs in shape for potential chases, despite what Tony and Kate thought, but other than that, he was more than happy to let his fingers do the walking...or delivering. Most of his paperwork came off his printer after he'd requested the electronic copy. Forensics paperwork, on the other hand, generally came from the source. He just couldn't help himself. He'd take any excuse he could to get down there. There was something so...cozy about it.
"Hey, McGee!" Abby yelled cheerfully over the pounding music that broke over his eardrums in crashing sonic waves as he entered the lab.
He waved in response, trying to cover his slight cringe. It was her space, after all. She could listen to her music as loud as she....
"All right, you can turn it down."
He looked abashed, but not surprised. After all, it was her job to notice little things. "I didn't ask...."
"Which is exactly why I'm giving you permission," she said, throwing him an impish grin. He smiled back and walked past her to turn down the speaker volume.
"I'm almost done writing up that fiber analysis," she called from her desk. "Ducky had a high priority tox screen he needed my help on."
"So you're stuck here late again tonight?" McGee asked as he settled into the chair next to her.
"Nope. Finished with Ducky, and in a few seconds"—she hit the print command with a flourish and the printer hummed—"I'm finished with Timmy."
"No hard feelings," she answered, handing him the freshly printed document.
"As soon as I get this up to my desk, I'm free for the night, too. Chinese at my place?"
"No can do tonight. I have a date."
He laughed, but stopped when she pressed her lips together apologetically. "You're serious."
"We were never exclusive, McGee."
"We were...I mean, I was...you...." He ran a hand through his hair. "Geez, Abby, are we past tense?"
"Oh, come on, please don't make me do this again."
"The DTR. Isn't our relationship defined enough?"
"Apparently not, if you've been non-exclusive all this time."
"It's not like I've been throwing wild pajama parties, I just like going out with interesting men."
"Oh, interesting men. I get it."
"That's not how I meant it, McGee, you know I think you rock."
"No, you're right. All I had to offer tonight was Chinese takeout. Where are you going?"
"This club downtown is having a costume party, and it's gonna be like a rave, and...."
"Say no more. Not a big costume guy."
"You totally could be, though." Abby bounced in her chair. "Why don't you come, too? We might hit a tattoo parlor later and get commemorative body art. I've always thought a bat tattoo would look amazing on your...."
He hung his head. "Wow."
"Abs, it's not me, okay?"
"You have that one tattoo already."
"That was for you," he burst out.
She smiled in satisfaction. "I kind of knew. That's so sweet, by the way. I think the bat should be right here," she said, tracing a circle on the left side of his chest, "or else you could center it more, and you'd be like my own personal superhero."
"In your own personal superhero league, you mean."
"Yeah, but you could be my favorite one."
He looked at her soberly, and all traces of teasing vanished from her eyes. "For how long?" he asked.
"McGee," she whispered, "don't make me...."
"No," he said. "I won't. I can do it myself." He took a deep breath. "Rule number twelve." He'd heard it often enough from Gibbs. Never date a co-worker.
"But if we aren't exclusive, it doesn't really count as dating."
He almost changed his mind then, when she gave him the loophole, except for one thing. "It counted for me." She opened her mouth to protest again, but he held up a hand. "You've never been happy with the idea of a long-term relationship. I've known that for a while. It was selfish of me to think otherwise." He bit his inner lip. "Calling it off now means we can be friends still. Right?"
Abby's eyes were red as she flung her arms around his neck. "Still and always, McGee."
He leaned into her, but jerked back when he heard paper crinkling. He looked at the document in his hand in confusion for a second before he remembered. "Better get this filed."
She nodded. "Okay. See you Monday?"
One door, two doors, three...and it ends with at least one whimper.