Too Many Loose Ends

What happened to Madeline? If she was killed, why? What does that have to do with Catherine's situation? Why does Catherine come onto Wolf in his room when delivering hangers and then later push him away when he tries to tell the truth of what is happening to her? Why does Wolf write an "M" in lipstick on his mirror? How is it the wine guy and his wife are the only ones not in the plot to steal Catherine's money and gradually kill her (I think) and how does Wolf know that he can trust them? Christian is onto Wolf, why not just dismiss him? Did Wolf know Christian was onto him? I could not make sense of this movie.