Daniel Tammet can recite pi to thousands of decimal places, do complex calculations in his head, and pick up a new language in a week. He is also autistic, a combination the film treats as scientifically rare: most savants with abilities like his cannot live independently, while Tammet can describe, in plain sentences, exactly what happens in his mind when he multiplies large numbers or learns Icelandic vocabulary. The film follows him to the United States, where researchers run him through cognitive tests, hoping his self-awareness might explain what produces savant skills in the first place and whether similar abilities lie dormant in ordinary brains. Along the way he meets Kim Peek, the savant whose life inspired Dustin Hoffman's character in 'Rain Man,' a meeting that puts two very different versions of extraordinary memory side by side. Tammet's epilepsy as a child is raised as a possible origin point for his abilities. The film stays close to the science being done on him rather than treating him as a spectacle.