Where can I find help dealing with an abusive spouse of a person with Alzheimer's?

My father in law abuses my mother in law in many ways. He does not feed her and she is dropping weight, he does not bath her or change her clothes and they are dirty and smelly. Her dentures havent' been cleaned in month. He has changed her financial wishes for his benefit. He drinks heavily, like 1/2 bottle of scotch each day. Where do I go for help.