Ninety-one-year-old Gretel Fernsby has lived in the same well-to-do mansion block in London for decades. She lives a quiet, comfortable life, despite her deeply disturbing, dark past. She doesn't talk about her escape from Nazi Germany at age 12. She doesn't talk about the grim post-war years in France with her mother. Most of all, she doesn't talk about her father, who was the commandant of one of the Reich's most notorious extermination camps.

Then, a new family moves into the apartment below her. In spite of herself, Gretel can't help but begin a friendship with the little boy, Henry, though his presence brings back memories she would rather forget. One night, she witnesses a disturbing, violent argument between Henry's beautiful mother and his arrogant father, one that threatens Gretel's hard-won, self-contained existence.