This article features the relationship between Mary and Matthew Crawley. Mary and Matthew came from different backgrounds with different social standings, Mary being of aristocratic blood and the eldest daughter of the Earl of Grantham, while Matthew was an upper middle class lawyer in Manchester.
Both the heirs of Downton, Mr James Crawley and his son Patrick Crawley, perish on the Titanic, leaving Lady Mary without an inheritance since the estate along with the earldom and Lady Grantham's fortune are entailed, which meant only a male child or near male relative can inherit which makes Mary very frustrated seeing as it is impossible to break it. Then a new heir is confirmed, Matthew Crawley, a distant cousin once removed of Lord Grantham's.
While Lord Grantham is welcoming towards his future heir, to somewhat degree Cora, the rest of the family such as Mary and Violet are hostile towards Matthew and his mother Isobel simply because they are middle class and not one of the aristocracy like them. Mary does not even like Matthew, and despises him as she believes he is usurping her inheritance. She often makes rude remarks about him and his life, even suggesting the idea of him being the future heir is a practical joke. However Matthew falls in love with Mary, despite her rude and snobby nature. Her family, who are now starting to get used to Matthew, try to pair them up for a possible marriage, but Mary wants nothing to do with him. However, Mary then ruins her chances of a suitable marriage after she beds the Turkish diplomat Mr Kemal Pamuk, who suddenly dies in her bed of a heart attack right after attempting to sleep with her.
Overtime, Mary and Matthew start to develop a friendship, with Mary joining Matthew at a local village fair where they discuss their lives. However Mary's opinion of Matthew begins to change after he rescues her youngest sister Lady Sybil along with the chauffeur Branson from a political rally in Ripon. Lady Mary praises him as very brave and the two bond over sandwiches. Matthew questions Mary about her tone of mockery towards him, and that those harsh words she uttered still remain on his mind as fresh as the day they were spoken. Mary then tells Matthew that he should learn to forget the things she says about him. With that they suddenly kiss, Matthew proposes to Mary. Mary tells him she will think about it. Her parents are delighted but Mary is reluctant to give him her answer, especially because her mother suddenly gets pregnant with a possible male heir and that she will have to tell Matthew of her scandalous liaison with Kemal - otherwise if Matthew found out, he would leave her.
On the advice of her aunt Rosamund, her father's sister, Mary decides to wait until the baby is born to give Matthew her answer, Rosamund wonders if Mary would even be happy with Matthew. Mary's long hesitancy hurts Matthew who confronts her and says that her decision should purely be based on whether she loves him or not. But Cora miscarries the future male heir. With this, Mary is now prepared to marry Matthew, but he says that she has taken too long to consider his proposal and he therefore retracts it saying he can't be sure of Mary's feelings towards him or of his future at Downton leaving Mary in tears. With that he leaves, but not before Robert announces that Germany has declared war on Britain.
It is World War 1 and Matthew is out on the battlefield. He and Mary do not speak for 2 years as he is out on front. He returns on a brief leave in 1916, when he and Mary renew their friendship, but he secretly saddens Mary when he introduces her to his new fiancee' Ms Lavinia Swire, whom he met on brief leave. Mary tries to hide her heartache by congratulating Matthew. Mary then later becomes engaged to Sir Richard Carlisle, a media proprietor and newspaper magnate tycoon who made his money as a ruthless newspaper company owner. He helps Mary to hide her scandalous story from the newspapers by making her promise that she won't jilt or leave him as he has the power to destroy her if she does.
When Matthew gets prepared to go back to war to participate in the Battle of Somme, Mary meets him at the train station, where she gives him a good luck charm of hers which is a stuffed dog from her childhood. She then kisses him on the cheek and asks him to take care of himself. Despite this exchange, the two keep their lingering romantic feelings to themselves as they are both engaged. Suddenly Matthew and his batman William both get caught in a terrible blast and fall into a muddy ditch with William selflessly protecting Matthew by falling on top of him but Matthew's back hit a wagon wheel behind him injuring his spine. Matthew and William are pulled out of the war, with William dying of his injuries not before marrying his sweetheart, kitchen maid Daisy on his death bed. Matthew is transferred into a hospital bed where Mary and her sister Sybil were waiting. Mary is heartbroken but is relieved that Matthew is still alive, she helps him recover by cleaning his injuries and wheeling him around on his wheel chair. She was delighted when he recovered but felt saddened when he and Lavinia announced their engagement at dinner.
The house then gets infected with the Spanish Influenza with Carson, Lady Grantham and Lavinia getting infected. While Lavinia is resting, Matthew is testing out their wedding present, a gramophone where he invites Mary to dance with him. Mary and Matthew talk about the past where Matthew apologises to Mary for breaking of his engagement to her and that he is marrying Lavinia out of sacrifice and duty. He and Mary then kiss, Lavinia sees and hears them but feigns ignorance of the episode. But later, she confronts Matthew with what she knows and says she doesn't want to go ahead with the wedding as he already loves Mary. Matthew asks her to reconsider but Lavinia asks him to let her rest which agrees to. Sadly Laviania's conditions worsens hours later and she dies telling Matthew that he would not have to make a hard decision regarding her or May as she knows she in on the brink of death, she tells Matthew that she wants him to be happy for her sake to remember her fondly. Matthew tries to reassure her but too late. Lavinia dies. Matthew is overcome with guilt at Lavinia's funeral and he tells Mary that he believes that Lavinia died of a broken heart because of them, and that any relationship between them is over. Mary understands and asks Sir Richard to walk her home.
Matthew has repaired his friendship with Mary,but it was blatantly obvious for everyone to see that the two are still in love, but her fiance Sir Richard is a threat. Sir Richard is extremely jealous of Mary's closeness with Matthew and tensions begin to escalate between the two with Sir Richard constantly demanding and threatening that Mary set a date for their wedding leaving Mary frustrated and irritated. Matthew presses her for an explanation regarding her continued engagement, with Mary telling him that he would despise her if she told him the reason why she had to marry Carlisle, and that she couldn't bear. Lord Grantham asks Lady Grantham why Mary still continues her engagement. Cora then finally tells Robert about the true circumstances regarding Pamuk's death in Mary's bed and how she and Anna helped Mary move his body back into his bedroom in the bachelors corridor. Mary confirms the truth with her father, Robert in his own way tells Mary to break off her enagement with Carlisle stating that he doesn't want his daughter to be married to a man who threatens her with ruin. Matthew also tells Mary that she must not wed Carlisle either, giving Mary the courage to tell Matthew about her liaison with Kemal Pamuk, although shocked at this information to begin with, Matthew tells Mary that he never would and never could despise her for it to which Mary is grateful for. Mary breaks it off with Carlisle leaving him extremely mad, Matthew fights for Mary by physically punching Carlisle in the face after Carlisle insults Lavinia. Sir Richard then leaves for good. At the Servants Ball, Matthew proposes to Mary again by saying that her scandal with Pamuk and his disastrous ending with Lavinia will never come between them and it is time they live their lives together. Mary is overjoyed but demands Matthew get on his knee and say his proposal properly which he does when he says in the falling snow "Lady Mary Crawley, will you do me the honour in becoming my wife?", with Mary happily saying "Yes", he stands up and he kisses her and lifts her up to hug her in the falling snow.
Lady Mary and Matthew are engaged but Downton is in financial trouble because of a bad investment made by Lord Grantham on a Canadian railway leaving Downton penniless. Matthew then learns that he has been named heir to his late fiancee's father's money but he refuses to accept it since he believes that he played a part in Lavinia's death which angers Mary, making her believe that Matthew does not care for them and will not save Downton and mulls over cancelling her wedding. However Matthew with some help from his brother in law Tom, help Mary to understand that they won't always agree but their feelings for each other are strong and neither of them would be happy with anyone else. Matthew and Mary wed and honeymoon in France. Matthew with some pressure from Mary, accepts Mr Swire's inheritance and invests the money within Downton, co sharing with Robert. Matthew then reads the books and sees that Downton has never been propery manged to begin with and pleads his case with his father in law who is resistant to let things change. But his mother in law, wife and brother in law support him making Robert agree to try out the modernising techniques of making Downton self sufficient. Like the rest of the family, Mary and Matthew are heartbroken when Sybil dies after giving birth to her and Tom's daughter. Mary and Matthew cannot have children biologically due to their respective issues, so Mary undergoes a successful operation to conceive a child within 8 months.
Mary is heavily pregnant, and the family are getting ready to visit their relatives in Scotland, Matthew and the rest of the family are worried about Mary's condition but she insists she is fine. Matthew and Mary then dance at the Ghillies Ball where Mary feels weary and says to Matthew that she will head back to Downton early, Matthew insists with coming with her but Mary refuses saying she wants Matthew to enjoy himself before he became a father. When Mary arrive sat the station, she goes into labour, her maid Anna and the train driver rush her to the cottage hospital where she gives birth to a healthy baby boy. Matthew is notified of the bay's arrival and is overjoyed in seeing Mary with their newborn son. He professes his everlasting love for Mary.
However when riding back home to tell the family about his newborn son, Matthew is speeding along the road without paying attention to anything and his car gets in a nasty crash with a truck throwing Matthew on the ground where the car lands on top of him. Matthew appears to have died instantly on the scene with blood trickling down his face.
Mary is unaware of her beloved husband's fate as she smilingly holds their son.