Leland Stanford and Eadweard Muybridge are both noted personalities of the late 1800s. Stanford was a grocer transformed into a railroad magnate who eventually became governor of California. Muybridge was a photographer who is credited with the birth of motion pictures, but also was involved in a sensational trial when he killed his wife's lover. Their stories converge when Stanford questions whether a horse's four hooves ever simultaneously leave the ground. It's Muybridge's stop-action photography that gives the answer.