During her youth, Mary was in a romantic relationship with Arthur Morgan and the two were deeply in love, but it ultimately fell through due to Arthur's life as an outlaw and affiliation with the Van der Linde gang , leading to prevalent disapproval from her family as a result, particularly her father. It is unknown if Mary ever met anyone in the Van der Linde gang through her relationship with Arthur. Abigail Roberts seemed to be the only one who took a liking to her.
Afterward, Mary eventually married a man named Barry Linton and took on his surname. Barry later passed away after contracting pneumonia, leaving her a widow. To make matters worse, her family grew to be dysfunctional as well; her younger brother, Jamie had joined Chelonia , an infamous fanatical cult, while her father gradually became more withdrawn and verbally abusive to his children, growing increasingly dependent on alcohol, whoring, gambling, and eventually began pawning off much of their family's property.
Mary contacts Arthur for the first time in many years and pleads for his help in convincing Jamie to leave the Chelonians. Arthur is apprehensive due to poor relations with the Gillis family but admits that he was at least on good terms with Jamie. If Arthur accepts, he successfully chases down Jamie and persuades him to leave the Chelonians, before taking him to Mary at Valentine train station.
Mary thanks Arthur for his help and then boards the train with Jamie to return home. After this, Arthur laments how he feels both elated and foolish for how Mary can manipulate him and resigned to the fact that he would not be able to refuse her.
He also writes his initials and Mary's in his journal with a heart between them. Mary later asks Arthur for help with her father, much to Arthur's ire. Mary begs for his help and tries to justify her father's poor treatment of him, but Arthur angrily points out that Mary's "pure life" hasn't fared well at all, referencing Jamie joining the Chelonians, Mr.
