Suspects a dear friend's wife has only married him for a passport, what can I do!!!?

I'm sure she didn't have her papers when she married him and now has them through a couple of years later!!!!!!! A friend has said so and she stays away for two weeks at a time after every week at home!!!!! Does not support him and never really talks to him at all, and dosnt go out with him and money keeps going missing from his bank account, he is english and she is African not sure what part she is from tho!!!! I'm so sure he is being taken for a ride and he cannot see it and I'm not the only person questioning it. Who can I call or contact and what is best to do, I'm afraid now she has her papers she is going to take everything from him or leave him in the lurch and he has just retired!!