Six weeks ago my mostly indoor cat wandered out of our yard and into the territory of another, aggressive cat. I believe she was forced away and cannot find her home since her territory was the back yard. I have done all the "people" things (newspaper ads, signs, network of cat searchers, etc.). What could a cat behaviorist tell me about how to find my beloved 6 year old cat?

Cats are smart and rather intelligent. More than what most people know. Your cat will come back in a couple of days or someone will bring him back through your methods of adverting. Try offering a reward if you haven't done so already.

Oh, with the other cat.. Put it down humanely with a hammer.