The film is based on Dava Sobel's book, Galileo's Daughter, which reveals a new side to the famously stubborn scientist - that his closest confidante was his illegitimate daughter, Sister Maria Celeste, a cloistered nun. In the film Simon Callow plays Galileo in dramatic reenactments of key moments from his life: his pioneering telescopic observations of the Moon and planets, his revolutionary experiments with falling objects, and his fateful trial before the Inquisition for heresy.