Irritated by a raucous Valentine's Day party in the admittance area as she comes on duty, Weaver attends to a few situations before entering the horrifying examination room where Carter and Lucy lie in massive amounts of blood, almost dead from numerous stab wounds. The police close off the crime scene and search the premises for the presumed attacker, Lucy's schizophrenic patient Paul Sobriki.

Benton helps Weaver perform an emergency tracheotomy on Lucy, but he must soon deal with Carter's possible spinal injury and uncontrollable internal bleeding from lower abdominal injuries. Barely regaining consciousness but aware of his situation, Carter takes comfort from Benton. Greene and Corday rush to the er after being paged during a night out with his father and her mother. They assist Weaver as she saws through Lucy's chest bone to repair her heart and liver wounds. But Romano and Corday must later remove Lucy's severely lacerated spleen. In the next operating room, Anspaugh convinces Benton to try another tactic before removing Carter's kidney; the maneuver works.

Finally, after Romano and Corday stabilize her, Lucy awakens. As she thanks the emotional Corday, Lucy suffers a pulmonary embolism. The doctors again open her chest to clear the clots. But despite their heroic efforts, Lucy dies. When Carter recovers, his relief at not being paralyzed is dampened by the news of Lucy's death. Gradually, Lucy's co-workers learn the terrible news as well.

During the chaos, Greene and Weaver realize that Paul got the butcher knife from a cake tray at the Valentine's Day party. The disoriented and paranoid Paul is soon brought in and arrested after being hit by a van while running naked from the hospital. As multiple trauma victims continue to arrive by ambulance, the mourning doctors go on with their work, minus one of their own.