Col. Ethan Willis joins the team as part of a program in which the Department of Defense sends doctors to hospitals to teach new techniques.

On Halloween night, Willis, Noa and Elliott rush to the scene of a fire at a haunted theater, where Dr. Nolan (Kathleen Rose Perkins) and her boyfriend's son are trapped.

The Angels Memorial doctors treat victims caught in a landslide, and a group of children come in from a camping trip with measles putting the entire ER at risk. Meredith Baxter and Eric Roberts guest star.

Malaya must inform a college student that she's been raped, while Willis and Campbell argue over a terminally ill woman who wishes to die on her own terms.

Willis and Campbell are sent to a Russian submarine in U.S. waters to treat a sailor badly wounded during an explosion, and violent convicts injured during a prison riot descend upon Angels Memorial.

The doctors treat cult members who unwillingly survived a mass suicide attempt, and Mario decides to connect with his late father's girlfriend.

A city-wide blackout leaves Angels Memorial without power or back-up generators.

Against Campbell's orders, Leanne uses the hospital helicopter to reunite a family one last time.

Guthrie considers an experimental surgery to treat his Parkinson's while adjusting to his new position as the hospital chaplain.

Mario follows Willis to a construction site to save two brothers trapped in a crane 300 feet above the ground.

A viral outbreak jeopardizes the doctors and patients of Angel's Memorial.

The doctors of Angel's Memorial partner with Center for Disease Control and Prevention to find an antidote for the viral outbreak.