How much does the human soul weigh? Marie is not normally the type to ask those sorts of deep questions. She works for Norway’s weights and measures institute, checking the precision of postal scales, petrol pumps and ski slopes. Her workdays follow a carefully calibrated routine; she studiously avoids contact with her ex-husband and her only human contact is with fellow workers. But when Marie’s father, the institute’s director, takes ill, everything changes. Marie must take his place on a trip to a seminar of experts gathering in Paris to discuss new ways of precisely determining the weight of a kilogramme. In her luggage, Marie carries Norway’s highly-valued prototype kilo, so that it can be weighed against its French counterpart. In Paris, she meets former scientist Pi and undertakes an emotional re-calibration of her own.