In a society that allows only two children per family, the so-called Thirds, the shadow children, live underground or under false identities. Nina Idi, accused of treason and subjected to tormenting interrogations, bravely faces her inevitable fate. However, the population police have something special planned for her. Nina is to act as a spy, eavesdropping on three imprisoned "third" children to betray their families. Her dilemma grows even greater when she comes face to face with her three fellow prisoners, who are only 10, 9, and 6 years old. Always huddled together, the three children appear distant and seem to have resigned themselves to their obviously hopeless situation. As Nina herself comes under increasing pressure, the three children present her with one riddle after another through their behavior.