I am having serious problems with one of my cats. To start off, I have 5, ranging from 2-11. Recently my 11 year old, Lexi, started pooping on a leather couch then followed it with urinating as well. The only reason I know which cat it is, is because we set up a recording webcam and caught her in the act. I also have a 5 year old male that is aggressive and does not really get along with the others. I found him when he was about 1 and he has never really meshed with the others. He chases the Lexi around and she is very stressed out from him. She can't even look at him without growling and hissing. Knowing that, we have separated them and put Lexi into her own little room when we cant watch her and see where she is going. We got rid of the couch, and watch her constantly and when we can't she is in the room with her own litterbox. I am at a loss of what to do next. I can't keep her confined, and Toby, the mean one, has gotten into bothering the others more and has become almost unbearable even for us. He bites you if you don't pet him on his terms, he bites if you don't put his wet food down fast enough.....etc. Since he (Toby) appears to be the problem, what would be my best course of action?