Harriet Brooks (1876-1933) was one of the first Canadian researchers in the field of radioactivity. Ernest Rutherford called her the best woman scientist in the field next to Marie Curie. She worked with Rutherford, J.J. Thompson, and Curie, and her achievements include identifying "emanation" (radon) and discovering the recoil of the radioactive atom. Yet, in spite of her contributions, this is the first biography of Brooks' life and work.