It appears that someone dumped a new cat at the barn. She's a real sweetie, will launch herself into a pet like its the best thing in the world... but we discovered her presence because she was stuck behind a stall wall.
Well, not stuck stuck, but she saw daylight through gaps and wanted out there instead of the end of the row of stalls. So we moved the horse, pulled the wall down, and pulled the cat out. Then put the wall back up and put the horse back.
Of course, before we started taking the wall down I had to reach through the gaps where some boards had been kicked loose and make sure she wasn't actually trapped, and that we weren't going to drop boards on her if we took the other ones out. But we got it done, and put back together.
Mystery Kitty is out, and eating and drinking... she's pretty skinny, but has a good healthy, shiny coat, so she hasn't been without food and water for very long. I think she's just naturally long and lanky, and missed a couple of meals, to get to where she's at now. She's also in heat. Thank goodness we got all the boys out there fixed.
We'll check on her tomorrow morning, and make sure she hasn't trapped herself again, but I think she felt a lot more secure after controlled introductions to the other cats. I wouldn't let them pick on her but as long as they were sniffing noses I left them alone.
It is interesting to note, however, that Smoke, one of the Pixel kittens that got me in so much trouble here at the apartment, is highly territorial. She really wanted to chase the rival female off, until "mommy" got stern with her.
By the time I left they were standing on either side of me, both getting petted, and completely ignoring each other.... they should be fine.