I asked Val to bring the carrier into the apartment, and as soon as Annabelle became aware there was a little cat inside, she started rolling around, almost flirting with Thatch, and then she tried to find a way into the carrier. Thatch started hissing and acting alarmed, as she climbed all over it looking for a way inside. So, I took Thatch out of the carrier and he and Annabelle faced each other and she watched him with much curiosity . There was no hostility, absolutely none, just a mutual casing of the other. she's now eating and he's finally come out from under the cat tree.
I'm going to let him roam for a bit and get his bearings. He's a very docile kitten, and really sweet. When his foster parents put him into my carrier, he was absolutely quiet while I filled out the paper work. His sister and the other fostered cat came to the carrier and said goodbye, then his sister, perhaps smelling Annabelle on my shoes and pants, played with my shoe laces.