I am chasing, hissing, growling and attacking my companion so much, that she has decided to stay in the basement and hide. If I see her, I chase her away. Grandma and Grandpa are very confused and feel bad about Unison being afraid to come upstairs. It would be so nice, if you could shed some light on my behaviour. Shelby Dear Shelby, I think the answer is in the fact that you have been allowed outside.
Cats are territorial.
When you were both inside all the time you have things divided up between you two and things were settled and happy. When you go outside, though, the territory changes. Suddenly there is a lot more space. There may be the smells of other cats about too to further mess things up for you two. Now when you go inside for some reason you are not content to share the space.