Tommy, a sixteen-month-old boy with Down's syndrome, is found drowned in a pond near his home. His young mother Carmen claims he wandered off while she and her husband were otherwise occupied. But something about the story doesn't ring true to Inspector Jacob Skarre, who turns to his trusted colleague, Inspector Sejer, for assistance. When an autopsy reveals Tommy's lungs to be full of soap, Skarre and Sejer revisit the couple. Carmen, an epileptic, changes her story, saying that she'd been knocked unconscious by a seizure while bathing Tommy. When she came to, she found him drowned in the tub and, horrified and frightened, threw him into the pond. As Carmen's own family turns against her, Skarre and Sejer are determined to get to the truth.