New York socialite Car­o­line Fer­ri­day has her hands full with her post at the French con­sulate, but her world is for­ev­er changed when Hitler’s army invades Poland in Sep­tem­ber 1939, with its sights set on France.

An ocean away from Car­o­line, Kasia Kuzm­er­ick, a Pol­ish teenag­er, sens­es her care­free youth dis­ap­pear­ing as she is drawn deep­er into her role as couri­er for the under­ground resis­tance move­ment.

For the ambi­tious young Ger­man doc­tor Her­ta Ober­heuser, an adver­tise­ment for a gov­ern­ment med­ical posi­tion seems her tick­et out of a des­o­late life. Once hired, though, she finds her­self trapped in a male-dom­i­nat­ed realm of Nazi secrets and pow­er.

The lives of these women are set on a col­li­sion course when Kasia is sent to Ravens­bruck, the noto­ri­ous Nazi con­cen­tra­tion camp for women. Their sto­ries cross con­ti­nents as Car­o­line and Kasia strive to bring jus­tice to those whom his­to­ry has forgotten.