A nanny reveals ways of making children behave that are much more effective than a time-out in this fantasy comedy based on the "Nurse Matilda" books for children by Christianna Brand. Near the dawn of the twentieth century, Mr. Brown (Colin Firth) is a widower who must tend to his business as an undertaker while looking after his brood of seven children. Brown's offspring are a singularly ill-mannered lot who have managed to drive away 17 different nannies when their father arranges for one Nanny McPhee (Emma Thompson) to help out with the children. McPhee is an strange looking woman with a large nose, protruding teeth, and pock-marked skin, but it isn't long before the kids realize she has magical powers and isn't afraid to use them to help keep them in line. While the children aren't taken with McPhee's insistence on such things as saying "please" and listening to their elders, it becomes clear everyone has bigger things to worry about. Aunt Adelaide (Angela Lansbury) has insisted that if Mr. Brown cannot find a new wife within a month, she'll take custody of one of the children and cut off Brown's inheritance, and while Brown and the widow Mrs. Quickly (Celia Imrie) seem fond of one another, his ineptitude in courtship seems to insure he'll never get her to the altar. But while the Brown Children realize Nanny McPhee is a formidable opponent, she can also be a valuable ally as they learn to make use of her talents by being better children; they also discover that as they behave better, she begins to look less frightening. Emma Thompson, who played the title role in Nanny McPhee, also wrote the film's screenplay.
by Mark Deming synopsis