My father-US citizen living in Karachi, Pakistan. After stroke, he has become mentally incompetent and step wife is not allowing him to visit US.

My father is a US citizen who is currently living in Karachi, Pakistan. Last year he had stroke due to which he has become mentally incompetent to make decisions. His step wife is giving us resistance to bring him back to US for proper medical care. I know this because I am a physician. When I visited him last year I saw signs of medical negligence. Due to his mental incompetence, his step wife is liquidating his properties and placing under her name. His step wife and her family has pretty much taken over his assets. When I visited him last week with my brothers, we did not even know where he lived until we found out through random sources. Once we met him couple of times, step wife took him somewhere in hiding. His step wife also threatened us by having thugs outside the house so we don’t return. She is also hiding his passport and not allowing any of family members to see him. Our father is in critical need for immediate attention for proper medical care. Any advice?