Disclaimer: I own nothing. "Angel" belongs to Joss Whedon/Mutant Enemy; "NCIS" belongs to Donald P Bellisario and Don McGill.
Timeline: Post-'Not Fade Away' for "Angel", and probably between seasons 2 & 3 of "NCIS".
"You're here! Welcome home!"
"Abby, we've talked about this-"
"I know, don't invite people in verbally. But I know you're safe!"
"And if I was evil?"
"You'd be wearing leather pants and a grin instead of shapeless slacks and your brood-face."
"Abby..." he trailed off warningly.
"Besides," the Goth woman continued obliviously, "I had to invite you in at some point in order to show off the new house. And, once I invited you in this time, you would have access at any time from now on anyway."
Angel was unable to argue her point. He wanted to, but she would have seen through the attempts easily. He nodded in acquiescence and stepped into the small house. It suited the woman, with comfortable-looking furniture in shades of black and red, hardwood floors and pale grey walls, and artwork that Angel recognized even with the odd colors.
"Is that a heart?" he asked, pointing to a framed piece hung above the mantel. "And a stake?"
"Yep!" Abby agreed. "Ducky let me bring the stake down and set it next to the heart before I took the picture. He thinks I'm still just being a vamp-obsessed Goth girl, but he's willing to humor me. Tony freaked out when he saw it. Well, after he recognized it, of course. At first he just wanted to know why a pick was nearly impaling a blue lump on a table. I had to explain about the heart being blue because it's cold, since it's been dead for so long, and the stake isn't actually touching the heart, yet; it's just resting against it. I call the piece 'Ending Threat'. See, because it could mean that someone's ending the threat that a vampire - not you, of course, unless you've lost your soul again - poses, or it could be a threat to end the vampire. So it has a kind of double meaning."
"It looks great, Abby," Angel assured her, as soon as he could get a word in.
"Oh man, it doesn't disturb you, does it? I didn't even think about that when I took the picture. Of course it would bother you! That would be like having a picture of just the wound Kate got when she... I mean, I'm so sorry. I can take it down!"
"Abby, it's fine. It shows off your creativity well; it suits you. Leave it up, please."
"Are you sure?" she asked uncertainly.
"Very sure. But that's not really the reason I came here. How are you?" Angel questioned her, staring into her eyes.
"Well, you know, I've been better. I mean, it's a little overwhelmingly male when I go to work now, but there's talk of getting a new female agent on Gibbs's team. It still won't be the same, though."
"It's not your fault, Angel."
"Nope. Not. Your. Fault," she told him, poking a finger against his chest with each word. She huffed in aggravation. That vampire would blame himself for everything wrong with the world if given half a chance. And he felt more at fault with any problem in her life than normal, since he remembered killed her family many generations previously.
Her many-greats grandmother was the eldest of three girls. When Angelus murdered all of the family but one sister, he did not realize that the oldest girl's husband and young son were with his family in France. Many years later, in Sunnydale, Drusilla made a comment about her young niece, coming from a world of silence, and dealing in death. After regaining his sanity when he got back from hell, he searched for the niece and found Abby.
After introducing himself, he and Abby grew close. When Sunnydale sank into a crater, Abby sent him a letter to offer any help he needed. He wrote back saying that he was alright, and that no one that he knew well had died in the collapse of the town. One year later, Angel found himself on her doorstep, bleeding and exhausted. He told her about the battle against the Senior Partners, and how he, Spike, and Illyria were the only ones to survive it.
Abby shared her life with the vampire she considered a great uncle. She told him about growing up with deaf parents, and they spent the next week using only sign language with each other. She called and invited him to spend the weekend with her when she got the job at NCIS, and again when she became the head of the lab. Kate's death was the first time she had called him needing emotional support after something bad had happened.
"I wasn't going to say it was my fault this time, Abby," he corrected after a moment of silence.
Angel smiled at her. "I was going to say that I'm sorry you have to go through this pain."
"It's part of living. Or, well, existing, I guess. Since you sometimes have to deal with pain too, and you're not technically alive any more."
"Still, it's not something I would ever want you to go through."
"Is there anything I can do to help?"
"Would you come to work and talk to Gibbs?"
"He hates me. And I'm not crazy about him, myself."
"But it's so funny to watch the two of you together," she giggled.
"How?" Angel asked with a frown.
"You're both trying to stake out your territory, but you don't want to make me upset, and so you just make these growly sounds while you're talking. I promised Tony that next time you were in town, I'd let him know early so he could bring in popcorn or something."
"I helped save the world multiple times. I am one of the two vampires who has ever had a living son. I was once one of the most feared creatures in existence, even. And now I'm entertainment for a couple of military agents. How did I sink so low?" he asked rhetorically.
"I think it was the gypsy thing. Your luck has been pretty bad ever since then."
"Got it. No gypsies, ever again."