The Duke other wize known as Zidler's invester, is a rich man, who, on his behafe feel in love with Satine, but, Satine loved Christian, and they hid there love from him, Which, he sortta figured, but, he didn't say anything because he didn't want to be wrong. The Duke, right after Satine & Christian falling in love, got a bit mad, but, they lied to him and said that thay were only rehursing for a play, That Christian then after wrote for the Moulin Rouge. When the Duke found out for good, he tried to rape Satine, and when id failed, he told Zidler to have Satine come back to him, or he would have the boy killed (The Boy is Christian). The Duke walks away from the Moulin Rouge finaly when Christian and Satine defy him and do their ending. He left not knowing that Satine died, right after the curtain closed.