Doctor Hallie Thomas was a resident at Lakeshore Hospital.When the show starts, she is engaged to Matthew Casey, but they are going through a rough patch, because he is eager to start a family, while she wants to wait at least until the end of her residency. After a period of separation, Matt and Hallie get back together and try to work through their problems. However, they break up for good in season 1, episode 7 ( Two Families ), when Hallie reveals that she doesn't actually want to have children at all.After the break-up, she takes some time off from the hospital and goes to do volunteer work in South America in order to find her inner self. A few months later, she returns to Chicago and starts dividing her time between Lakeshore Hospital and a free clinic.She makes a surprise comeback in Matt's life in season 1, episode 20 ( Ambition ). The two of them reconnect and seem very happy to be back together. That doesn't last though, because the clinic where Hallie works catches fire. Although Casey does everything he can to save Hallie, she succumbs to her wounds by the time they get her to a hospital.