Widower Cedric Brown (Colin Firth) hires Nanny McPhee (Emma Thompson) to care for his seven rambunctious children, who have chased away all previous nannies. Taunted by Simon (Thomas Sangster) and his siblings, Nanny McPhee uses mystical powers to instill discipline. And when the children's great-aunt and benefactor, Lady Adelaide Stitch (Angela Lansbury), threatens to separate the kids, the family pulls together under the guidance of Nanny McPhee.