Claudia, recovering from cancer and sharing custody of her 12-year-old son Rhys, works as a primary school nurse and struggles to find meaning in her life. She tries in vain to help Imogen, a little girl she fears is being mistreated at home, but when she stumbles upon a search for five-year-old Emily Winter, who's gone missing from the playground on her street, Claudia is inescapably drawn to Emily's parents Owen and Sabine. As Claudia's obsession with the case grows, she forges a relationship with mysterious George, an English teacher at her school and finds herself in the midst of a deepening mystery.