Abigail Marjorie Lockhart, M.D. (née Wyczenski) is a fictional character from the NBC medical drama series ER, portrayed by Maura Tierney. Usually referred to as simply Abby, she first appears as a guest star in the first half of the sixth season, before becoming a main character later that season, appearing until the beginning of the fifteenth season. Tierney returned to make one final guest appearance later in season fifteen. Beginnings The character Abby Lockhart first appears in season 6 of ER in the episode "Great Expectations", guest starring as Carol Hathaway's (Julianna Margulies) labor and delivery nurse. Three months later, she became a regular character. She first made an appearance in February 2000 as a third-year medical student beginning her ER rotation. On her first day, she meets Dr. Luka Kovač (Goran Visnjic), her first teacher, with whom she will experience a number of professional and personal relationships and who will become the most important character in her long-running story. Lockhart's first months in the ER prove challenging for her transitioning from OB nursing to the ER. In that time, she sees Carter stabbed and a medical student, Lucy Knight, killed by a patient with schizophrenia , and also has to speak to superiors Kerry Weaver (Laura Innes) and Mark Greene (Anthony Edwards) about John Carter's (Noah Wylie) growing drug addiction. Although Carter is hostile at first, he and Abby become friends over the course of the next season. Abby's medical training had gone into hiatus and she had become a full-time obstetrics nurse to provide for her then-husband Richard Lockhart's medical school education, but once they divorced she resumed her medical training. At the start of season 7, Weaver breaks the news to her that her registration for her final year of medical school has been denied due to lack of payment. Abby confronts her ex-husband who has stopped paying her tuition because he is bankrupt. She resumes her part-time OB nursing job, and soon Weaver offers her a full-time ER nursing position. Abby accepts the offer. After several generally rewarding years as a nurse, Abby gets her ex-husband to sign off on a loan so she can finish medical school. The loan defaults, but John Carter pays the deficit. While she fails her first board certification exam, she passes on her second try, and she earns her MD in the Season 10 finale. At first Abby is