Flo and Kay are identical twins, both autistic savants, both able to name the day of the week for any date in their lives and recall the weather and even breakfast from decades back. At 52, they are sociable and bubbly, passionate about music and gigs, which sets them apart from the usual autism stereotype the film sets out to dismantle. Psychologist Dr David Holmes visits the sisters at home and reads their obsessively tidy routines as the source of their calendar calculations: order in the house, he argues, produces order in the mind, and both feel more secure the more of it they can build. At the New Jersey Neuroscience Institute, Dr Nancy Isenberg runs Flo and Kay through the Autism Diagnostic Observation Schedule, asking them about friendships and emotions while watching how they sit, gesture, and respond. The film sits between the two kinds of evidence, the twins' own daily lives and the clinical assessment trying to explain them, without fully resolving how the calculation happens.