I have two indoor 5 year old Calico sisters that have been together since birth. They usually get along great and we have had no problems in the past with fighting (other than horse play). Two days ago one was admitted to the vets for a urinary tract infection and spent one night there. She returned home yesterday (Sunday) and the other sister freaked out. She won't go anywhere near her sister and hisses at her on sight. Last night they slept in seperate bedrooms and today there has been no change. We thought it might be a scent that the one sister picked up at the vet so we gave her a quick bath but that made no difference. Has anyone else had this happen to them? Does anyone have any suggestions? Thanks!