In this dark and witty fable, Emma Thompson (Harry Potter and the Prisoner of Azkaban, Love Actually) portrays a person of unsettling appearance and magical powers who enters the household of the recently widowed Mr. Brown (Colin Firth - Bridget Jones's Diary, Girl with a Pearl Earring) and attempts to tame his seven exceedingly ill-behaved children. The children have managed to drive away 17 previous nannies but as Nanny McPhee takes control, they begin to notice that their vile behaviour now leads swiftly and magically to rather startling consequences.