The life of New Yorker Caroline Ferriday changes forever when Hitler's army invades Poland in 1939. An ocean away, Polish teenager Kasia Kuzmerick sinks deeper into her role as a messenger in the Polish Resistance. In Germany, young doctor Herta Oberheuser starts her career full of ambitions but soon finds herself trapped in the male-dominated Nazi regime. The lives of the three women intersect when Kasia is sent to Ravensbrück, the notorious Nazi concentration camp exclusively for women.

The book is based on the true story of the "Rabbits," the women who managed to survive the tortures at Ravensbrück, and reveals a shocking story of love, redemption, and heinous secrets that remained hidden for decades.