Kovac defies the rules to get a dying Croatian boy to Chicago in a race to save his life. Despite receiving tragic news, Carter tries to prevent grieving gang member Curtis from seeking vengeance. Carter's sad family gathering is interrupted by Abby's mentally troubled brother Eric, who has left his voluntary care facility. Meanwhile, Lewis has trouble ending her relationship with Chuck. Perez, a baseball player with a serious heart ailment, is treated on the eve of his pitching debut with the Chicago Cubs. And a tormented Romano makes a dramatic decision about his mangled arm, after it catches fire in his kitchen. Luka departs for the Congo after saying goodbye to Abby.

Carter travels to the Congo to join Luka, and quickly discovers how different things are to what he left behind. When an overdue Luka returns briefly from a remote clinic, we learn he's having a cozy relationship with French-Canadian nurse Gillian. Carter, Gillian and two aids join Luka at the clinic in order to set up an immunization program. They soon find themselves caught between the Mai-Mai and the Congolese army with several patients, among them an injured young girl and her mother. When the group must evacuate the clinic, Luka refuses to leave his patients and remains behind. Carter returns to Chicago, going to a sleeping Abby's bedside.