So, kitties... we did not remotely anticipate what happened there.
The person fostering them brought them to our house last week, and introduced them. Two sisters, a little over a year old, both sweet, beautiful and super-soft. She brought them out of their carriers, since they showed no signs of leaving on their own. Then they both made a beeline for the laundry room, and got behind the washer.
We moved the washer and pulled them back out, and then the woman held each of them and petted them, and gave them to us one at a time. The cats were clearly scared, but not aggressive. We talked, stroked the cats, and let them wander (right back into their carriers, as it turned out). Then the woman left. All of this took more than an hour.
I showed the cats their litter box and food and water, and gave them gentle, reassuring pets. Then we left them alone in the kitchen for a bit. After a while, I heard the sounds of one of the cat toys moving, and when I went into the kitchen about ten minutes later, they had disappeared.
We'd blocked off any access to behind the washer and dryer, and could see they weren't back there. After much, much searching, we found them in the narrow space between the fridge and the wall, where one of the cats was using her sister as a pillow.
They stayed there the rest of the day, until the kitchen was dark and empty, and I heard them break something around 10:30pm. I relocated them to the laundry room, which made them both nervous.
The next morning, they were hiding next to the fridge again. We couldn't coax them out with treats or toys or pets. They moved again around late evening, so I blocked off access to that space. But the next day, the shyer cat was behind the dryer again. She stayed there almost the entire weekend, only coming out when the dryer was actually on or when no one else was around.
The other cat got to the point where she would come out to see me, and spent time cuddling and playing when HalfshellHusband wasn't around (he's heavy-footed, and talks louder than I do, which both cats found scary). That kitty was kind of a tiny terror-- really energetic and full of mischief, but really, really cute. But still kind of skittish.
Her sister never got over being petrified. :(
If it had just had the one cat, we would have given it at least another week to see if she could get over being afraid of HSH. But her sister was a lost cause. After five days, she was still doing everything she could to avoid us.
This is what we didn't expect, and what the foster owner wouldn't have guessed. Both cats had bonded with her, and were sweet but clearly shy. But they'd never been in a situation before where she would have been able to tell that they were pathologically shy. This was a first for me, too. Cats like me, and even the shy ones warm up to me. But one of them was clearly unadoptable, and we couldn't keep one without the other. If the friendlier cat had come on her own, yes. But we couldn't have the foster owner come back and take only one of them home. That would've been too awful for both cats. So, we had to give both kitties back. :(
There may also be a lesson in here (that we've encountered before) about not adopting siblings, because they bond with each other and not with you. But having never adopted from a foster home before, we now wonder if that might also be a mistake. A cat you bring home from the pound (or a tree near your office) is desperate to find a loving family. They know they're being rescued. But a cat that is already in a loving home is more likely to feel traumatized or sad about being re-homed, rather than grateful.
So, no kitties after all, not just yet. But we'll keep looking, and hoping that someway we'll find the right match for us.