A "Safe Room" needn't even be a separate room, but could be an empty closet, a corner of your bedroom with a protective screen, or a seldom-used bathroom. The important thing is that your new cat has a place he can call "home," where he can retreat and rest. He may voluntarily choose to socialize with you and other family members, but for now, let him decide whether to hide or mingle. It may take several days to a week or more, depending on his history, but your patience at this point will yield exponential results in a happier relationship with your cat in later days.
