Mary's relationship with the new heir, distant cousin Matthew Crawley, begins coldly as she overhears him complaining to his mother that he expects the family will "throw" the daughters at him. Over time, however, the pair grow closer and a romance develops. In 1914, Matthew Crawley asks Mary to marry him, but she is cautious and says she won't give him an answer until the end of the London Season in August. However her mother becomes pregnant, and if the baby is a boy, he will inherit the title instead of Matthew, so Mary refuses Matthew on the advice of her aunt, Lady Rosamond. Matthew is quick to grasp her reasoning and leaves Downton for a time. While he is away, Mary gets engaged to Sir Richard Carlisle, a newspaper magnate who, when Mary confesses to it and asks for his assistance, promises to help keep the Pamuk affair under wraps. They plan to marry in July 1919, after the marriage of Matthew and his new fiancée Lavinia, and to move to a neighbouring, stately home that Sir Richard plans to buy. After Lavinia's death, it becomes clear that Matthew and Mary still have feelings for each other. In 1920, Mary breaks off the engagement to Sir Richard and initially agrees to move to America to live with her grandmother and maid Anna. However, Matthew again proposes to her on bended knee, and the two get engaged.
Duke of CrowboroughEdit
Unfortanatly for Mary, the Duke of Crowborough is only interested in her for her money and the estate. Mary is very disappointed and takes her anger out on Edith(no surprise there!)