Multiple traumas come to the ER after a truck crashes into a coffee bar, narrowly missing a very pregnant Carol. Romano becomes Chief of Staff when Anspaugh announces his retirement. Weaver becomes even more unpopular when she is appointed permanent Chief of the ER by Romano. When she becomes engaged to Reggie, Jeanie decides she wants to adopt an HIV-positive baby. Two new staff members are introduced: Luka Kovac, a Croatian doctor moonlighting in the ER; and Cleo Finch, a pediatric resident in the ER. The ER is thrown into chaos when a patient pulls the fire alarm.

Mark clashes with new attending physician Gabriel Lawrence. Lucy and Luka try to convince a woman that her husband is dangerous. Carter tries to be supportive as Elaine undergoes her mastectomy. After Weaver puts in a good word for her, Jeanie receives baby Carlos on a temporary basis; she and Reggie get married later in the day. Cleo treats a family who was in an accident. Benton talks with his lawyer about having a DNA test. Mark and Elizabeth spend their first night together.