Lilac Girls is a historical fiction novel by Martha Hall Kelly. Published in 2016, Kelly’s debut novel is inspired by the true story of New York City activist and socialite Caroline Ferriday. Kelly was also inspired by the true story of the Ravensbrück Rabbits, a group of Polish women who were victims of torturous medical experiments during the Second World War. The novel explores the themes of hope, sacrifice, and forgiveness in the face of injustice and impossible circumstances. Lilac Girls tells the stories of three women during World War II: Caroline Ferriday, Kasia Kuzmerick, and Herta Oberheuser.

The novel begins in 1939 with Caroline and continues to alternate perspectives with both Kasia and Herta. At the beginning of the novel, Caroline is a New York City socialite who works for the French Consulate. She is an active member of the French Families Fund charity and frequently puts together comfort boxes for orphanages in France. While working, Caroline meets a French actor named Paul Rodierre. They are immediately enamored with each other, but Paul is married to a French woman. Across the ocean in Poland, Nazis have invaded Lublin, and 16-year-old Kasia’s world has been turned on its head. Kasia and her two best friends, Pietrik and Nadia, begin working for the underground, a radical resistance group working to destabilize Nazi control. In Germany, Herta Oberheuser is a medical student who is intensely loyal to the Reich. She is deeply anti-Semitic and apathetic to the plight of others. Herta is not allowed to be a surgeon because she is a woman. Herta struggles to find a medical job and eventually gets a position at a labor camp called Ravensbrück; she takes it to get away from her Uncle Heinz and his sexual abuse.

Caroline and Paul become more romantic and flirt with the idea of being together. Paul returns to France, however, as war veers ever closer. Caroline worries that she may never see him again. After he leaves, Caroline works tirelessly to get visas and immigration quotas raised in the United States. Kasia gets caught while carrying out a mission for the underground. The SS takes Kasia, her family, and Pietrik as well. The women are taken to Ravensbrück concentration camp where they are subject to all horrors of abuse and torture. The months continue on, and Kasia’s mother, Halina, becomes Herta’s assistant. Herta takes a shine to her and for a while, Halina is able to sneak food to her daughters. 

Soon after, war breaks out in earnest. Herta is ordered to perform medical experiments on the women in the camp. Kasia’s leg is broken deliberately, Zuzanna is sterilized, and other women are similarly experimented upon. Luiza, Pietrik’s sister, dies as a result of these experiments. The women are given the nickname “rabbits” as they are mostly only able to hop and are treated like lab rats. The other women in the camp rally around the Rabbits and hide them from the soldiers, give them food, and help them around the camp. Kasia develops a system to send secret coded letters to her father. She writes in her urine and tells him to send back red thread if he can read her message. He does. Halina’s mother is missing, and everyone knows she is likely dead. Herta is distraught by the news but pretends otherwise.

Germany loses the war. Caroline finally receives a letter from Paul. She nurses him back to health in Paris and they resolve to be together. Rena, thought to be dead, returns and reveals that her and Paul have a child. Caroline is distraught, but she helps them find their daughter. Kasia and Zuzanna are to be sent to the shooting wall. The Swedish Red Cross is there that night, and the other women coordinate a blackout; the sisters pretend to be French and are rescued. Herta flees on foot to Düsseldorf, where she is apprehended despite her attempt to kill herself.

Kasia finds her first love Pietrik and they marry; they both are still dealing with the trauma left from the war, but they find solace in each other. They have a daughter they name Halina. Caroline returns to New York, heartbroken, where she learns about the Rabbits. It has been 10 years since the war, but Caroline starts a charity to bring them to the United States for medical treatment. Kasia, Zuzanna, and Caroline finally meet. Zuzanna stays in America and marries Serge, Caroline’s chef; they adopt a baby boy named Julien. Caroline meets Paul and his daughter, Leena. Leena invites Caroline to Paris, and she is unable to refuse. They rekindle their relationship.

Kasia is unable to connect with her husband and daughter. She is furious at the injustice that she faces and is unable to move past the death of her mother. When Caroline tells her that Herta Oberheuser has been released from jail 15 years earlier than her sentence, Kasia is livid. Caroline gives her mission: Kasia is to positively identify Herta so that she can be stripped of her medical license. Kasia goes to Stocksee, Germany, and confronts Herta. Kasia learns the truth of what happened to her mother—her mother was shot for trying to aid the women and prevent further surgeries—and finally gets back the ring Herta stole from Halina. The novel ends with Kasia finding peace; she writes to Caroline confirming Herta’s identity and returns home to reunite with Pietrik and her daughter at last.