I do hope I've posted this in the correct section but if not I apologise and feel free to move. Please forgive my ignorance here but I really need some advice about my 3 year old spayed cat. I've had Toots for about 2 years now after rescuing her from a bad home and up until yesterday I've had absolutely no problems. Firstly let me explain that I live in a bungalow and have trained Toots to go in and out of the bedroom window rather than have a flap fitted. Anyway she was sitting on her window cill mat as per usual when suddenly she starting spitting and wailing, I opened the window to let her out and she shot out like a bat out of hell, I did spot another cat in front she was chasing, both disappeared and that was that. Later she rang her bell (I have a little bell by the window that she rings when she wants to come in) I let her in but saw this other cat outside hanging around but thought nothing of it. All was quiet until approximately 2am this morning when I was awoken by the wailing and spitting again, at which point, I looked out and saw this other cat, Toots was going doolally so I picked her up and put her in the lounge and shut the door and left her in there for the night. Tonight, this other cat has appeared again and as I type Toots is wailing and making odd noises, occasionally spitting and jumping up at the window. I've no idea what's going on - can anyone give me any ideas please? Apologies for the long first post.