Oh long story, Topper has been here about a month. He originally attacked Shadow and caused him a lot of pain. I have kept them separated once again for about 3 weeks, only seeing each other through glass (Shadow is partly outdoor kitty) and they would see each other and Shadow would hiss and the other cat would meow. Topper is VERY skiddish and any little sound scares him and I think that is part of the problem. But i have heard from 2 behaviorists that if you put one cat in the carrier and the other not it makes them both defensive (I only have one carrier). Shadow wont even go near the door where the other cat stays. I held him in my lap so that he could smell a little under the door (while he was hissing) and I could just hear him sigh so heavily, I am worried about the stress it is causing them. Any other ideas I havent thought of yet??