The staff unites to save one of their own. A former slave turned activist arrives in town, causing a rift between Foster and Mary. The Greens are in disarray; Emma and Frank's romance ignites and Samuel plans for a reunion with Aurelia.

A house guest becomes the focus of Alice's schemes. When Mary falls gravely ill, Foster's attempts to care for her antagonize the new chief. Charlotte tries to contain the smallpox epidemic and Samuel has to make a difficult decision.

As Pinkerton looks at the Greens more closely, they join forces to hide an ugly secret. McBurney, hoping to distance Foster from Mary, sends him to a nearby army camp on a house call. Alice helps Frank escape and Samuel earns Charlotte's respect.

After the Second Battle of Bull Run, Hopkins and Emma set out to rescue a stranded group of wounded Union soldiers. Lisette, a hospital observer, discovers the truth about a young soldier, shocking Foster. Hopkins and Emma share an intimate moment.

Lisette re-creates on paper the face of a disfigured, amnesiac soldier, leading to a family reunion. When Anne's plans to be made head nurse fail, she rejoins Hale to undermine McBurney's authority. Pinkerton questions the Greens, causing a rift.

After Antietam, the Greens suffer a setback and Pinkerton's inquiry heats up. Foster and Samuel visit Foster's family plantation, where they intervene in a difficult labor. The hospital staff unites to oust their hated chief. In Boston, Mary's condition worsens.