Stephen Hawking narrates his own life story, from a Oxford childhood and Cambridge doctoral years into the diagnosis, at twenty-one, of the motor neuron disease that doctors expected to kill him within a few years. The film follows him instead through five decades of it, tracking how the disease's slow paralysis coincided with his most productive scientific period: the work with Roger Penrose on gravitational singularities, the theoretical prediction now called Hawking radiation, and his years as Lucasian Professor of Mathematics at Cambridge, a chair he held from 1979 to 2009. Archival footage and home-life material show the physicist behind the wheelchair and the voice synthesizer, married twice, raising three children, and writing A Brief History of Time, a book that stayed on British bestseller lists for 237 weeks despite its subject. Hawking speaks throughout in his own synthesized voice, giving the film a first-person account of what it is like to do cosmology while losing the physical ability to speak, write, or move.