Nurse Lockwood gets arrested when she takes a stand. Meanwhile, Dr. Halstead deals with a pending lawsuit against him; a baby's injuries come into question; Dr. Charles faces personal issues; and suspicions rise about a patient who was hit by a car.

Dr. Rhodes treats his mentor and Goodman faces personal issues in the Season 1 finale. Also: April deals with a disorderly patient; Dr. Manning's past catches up with her; and Sarah's graduation day arrives, but she remains conflicted about her future.

The hospital is forced to evacuate when a toxic chemical is brought into the E.D., leaving patients and the staff in grave danger. Stuck in an elevator, Dr. Charles and Dr. Manning are forced to take drastic measures with a pregnant woman. Goodwin is tasked with making difficult choices and Dr. Rhodes discovers a secret that Dr. Bekker has been holding from him.