As the story opens, Mr. Brown (Colin Firth) is very inadequately dealing with his seven children, who are acting out VERY badly in reaction to the death of their mother and their father's distraction. The children have driven off seventeen nannies in a few months, and the local nanny agency has backballed them. Brown's Aunt Agatha (Angela Lansbury, channeling the late Hermoine Gingold) has accurately determined that things are out of control, but tryannically declares that unless Brown remarries within the month, she will cut off the financial support that is keeping the family afloat, and, moreover, attempts to "help" by taking one of the girls to live with her.
Enter Nanny McPhee, who literally shows up on the doorstep. Thompson bravely hides her beauty under the very grotesque makeup of McPhee, including hair-growing raised moles (inaccurately refered to as 'warts'), severe rosacea, a Frida Kahlo eyebrow, teeth badly in need of orthodontia, and a tent-like dress of widow's weeds. The collection of prosthetics limit's Thompson's range of expression in the early scenes, but, since this is the stage at which she is most stiff-upper lip formidable, it does not hurt too much.
McPhee proceeds to take charge in no uncertain terms, with harsh use of her magic that turns the childrens' antics back upon them. Meanwhile, Mr. Brown, obedient to Aunt Agatha's decree, decides to offer marriage to the one available woman in town, the widow Quickly, a monster of bad taste who promises to be everything the children dread in a stepmother.
While the ultimate solution to the dilemma is fairly obvious early on, the plot takes several twists that make the outcome work out in a surprising way. Nanny McPhee's magic use grows more subtle as time passes and her lessons are received. I particularly liked the way the children have to start taking responsibily for making decisions and the consequences of their actions, but would have like to see more involvement of the children other than just Simon (Thomas Sangster), the oldest boy, in the decision-making.
The story is a generally charming script, set in a mildly weird Victorian never-never land. The initial impression of the Browns' house, with its tempera-colored walls, is that the children painted it, until we see Mr. Brown's business--he is an undertaker, and he and his rather gay (in both senses--) assistants, are producing lavender coffins for their clentele of stuffy looking dead old men. Mrs. Quickly's house is a virulent-colored travesty that matches her day-glo Limoges shepherdess outfits.
Fun performances by all the cast, including Celia Imrie, who's wonderfully awful as the Widow Quickly, and veteran actors Sir Derek Jacobi and Patrick Barlow cavorting as the undertaker's men.
Nanny McPhee's initial uses of magic could be frightening for younger children. Older children will get a hoot out of the movie--but use caution, they may pick up ideas on how to be very naughty indeed--.