Ruth, who is from Edinburgh, Scotland, comes from a strict Presbyterian family headed by a minister father. She comes to London with her friend Anna, because she does not want to comply with her father's ideals. Anna contracts HIV, and Ruth is first seen in July 1994, visiting her at a hospice. There, she meets Mark Fowler, who has HIV. She and Mark bond, and he comforts her when Anna dies. They start a relationship and she becomes a childminder. In 1995, they get engaged, and Ruth's father insists that they marry in Scotland but her family are not welcoming when they discover Mark's HIV status. They respond with trepidation and ignorance, refusing to distinguish between AIDS and HIV, despite Mark's best efforts to explain. Believing he is contagious, they do not let him stay in their home, suggesting that he represents everything they have spent their lives battling. Ultimately, Ruth and Mark marry without her parents' blessing.
They soon start to argue because Ruth although she tells Mark she is happy about not having children, this is not true. They visit a counsellor who tells them their options, and they decide to be foster parents. They are given their first foster child, 6-year-old Jessie Moore, whose mother is in prison on remand. Jessie refuses to speak and wets the bed. Mark and Ruth try to get her to engage with them and they eventually make progress. Ruth returns to Scotland to visit her father, who has had a stroke. While she is away, Jessie receives a letter from her mother, saying she will be released from prison. When Ruth returns after her father's death, she is furious that Jessie has visited her mother in prison and will probably be returning to her mother soon. Ruth and Mark argue and Ruth grows closer to Mark's cousin, Conor Flaherty, who is staying with them. Jessie's mother, Nicole, visits and tells them she is taking steps to get Jessie back. When Mark and Ruth try contesting Nicole's decision, they are told that fostering is about reuniting children with their parents. Both become depressed and Mark's jealousy over Ruth's relationship with Conor makes things worse. When Jessie returns to Nicole, Mark and Ruth's relationship declines swiftly. Amidst constant arguing and jealousy, Mark moves out. Ruth gets drunk and tries to seduce Conor but he turns her down, admitting to finding her attractive but he says he cannot have sex with someone whose previous partner is HIV positive and berates her for being irresponsible. Ruth is deeply offended, and when Mark finds out what has happened, he declares that their marriage is over.
Ruth spends much time partying, clubbing, and enjoying her freedom. Her wild behaviour attracts barman Huw Edwards, but she rebuffs his advances. Eventually, Ruth's partying and neglect of her property means she cannot pay her bills. Mark's mother, Pauline Fowler, gives her money hoping that she and Mark will reconcile but it becomes clear that this will not happen. Ruth begins an affair with Conor, but after they have sex, he worries that Ruth will get pregnant and insists she take the morning-after pill. Ruth protests and eventually lies that she has taken it. The affair ends but she is pregnant. When Conor's daughter Mary Flaherty accidentally tells Mark this, he is furious and beats Conor up and informs him of the pregnancy. Conor suggests he and Ruth resume their relationship and bring up the child together but she refuses, choosing to be a single parent and returns to Scotland, rejecting Mark and Conor as she leaves. Soon after, Conor and Mary leave Walford, looking for Ruth.