Nanny McPhee's (Emma Thompson) motto is always the same: "When you need me but do not want me, I must stay, and when you want me but no longer need me, then I have to go." Also pretty close to being the same: "Nanny McPhee Returns," a sequel to 2006's "Nanny McPhee" that uses an identical formula with basically the same results. As directed by Susanna White and written by Emma Thompson herself (based upon the "Nurse Matilda" book series by Christianna Brand), this redux strengthens a few elements—the children, for example, are better developed and not so interchangeable—while falling victim to most of its predecessor's failings. Most disappointingly, the title character is as enigmatic as ever, basically a magic-weaving onlooker to the people and conflicts around her. She never really forms a strong relationship with any of her charges, thus negating an ending that requires that they want Nanny McPhee, but no longer need her.

With her husband away at war, harried mother Isabel Green (Maggie Gyllenhaal) has her hands full, taking care of children Norman (Asa Butterfield), Megsie (Lil Woods) and Vincent (Oscar Steer) while keeping up with the family farm and working a stressful job on the side for dotty old shopkeeper Mrs. Docherty (Maggie Smith). With snooty, wealthy young cousins Cyril (Eros Vlahos) and Celia (Rosie Taylor-Ritson) coming to stay with them for a spell and none of the children getting along, the person Isabel needs is Nanny McPhee. Sure enough, the forthright, disheveled Nanny shows up at their door, sweeping in and assuring Isabel she'll whip them all into shape in no time. As Isabel deals with pushy brother-in-law Phil (Rhys Ifans) pressuring her into selling the farm, Nanny sets her sights on teaching Norman, Megsie, Vincent, Cyril and Celia five lessons that will not only correct their rowdy behavior, but help to build their character.

"Nanny McPhee Returns" is a harmless trifle, sure to entertain children even if it's not presenting them with anything particularly fresh. The tone is light and loopy at the onset, reminding of a live-action Disney film from the 1960s as the characters act in animated ways and comic relief comes in the form of a belching black bird and various other slapstick scenarios. Far too much pronunciation is put on baser ploys to pander to the single-digit set—there is enough material dealing with poo to last a lifetime, and a scene where CGI pigs prance on tree branches before performing a synchronized swim feels unnecessary and tacked-on—which do expend a lot of one's good will. Also egregious is Nanny McPhee's propensity for gradually becoming more attractive as the children she is caring for learn each lesson she teaches, her moles and blemishes disappearing one by one. Why does this occur? Isn't it sending out a negative message to impressionable younger viewers that physical beauty is as important as one's moral compass?

Emma Thompson (2008's "Last Chance Harvey") keeps letting herself down as Nanny McPhee; after all, she is the one who is writing the scripts and continues giving herself little to do in the role. The character has a great, distinguishable look, but she's painfully one-dimensional, always seeming to stand at a distance from the rest of the film's participants and failing to ingratiate herself into their lives as a genuine friend and confidante. This time, Thompson is even more overshadowed when placed next to Maggie Gyllenhaal (2009's "Away We Go"), an utter delight as Isabel Green. With her slightly broad British accent and mannerisms, Gyllenhaal impeccably captures the light, silly feel director Susanna White is aiming for without going into caricature. When things turn more serious after a key plot development in the second act, Gyllenhaal is just as assured in reeling things back and going for the emotional truth of the situation. It's a performance far deeper and more memorable than the project deserves. The five youngster portraying the children, all of them newcomers save for Asa Butterfield (2008's "The Boy in the Striped Pajamas"), are startlingly confident, almost overly so. They are quite good in their respective parts.

"Nanny McPhee Returns" is at its best when Norman and Megsie are coming to terms with not knowing whether their beloved soldier father, who hasn't wrote them a letter in three months, is safe, and when Cyril and Celia are coping with distant parents who replace their affections with material possessions. Even if the war itself is lightly tiptoed around—no mention is made that it is even World War II, but the evidence points to such—the real-world dealings within the story are presented in a classy way that avoids heavy-handedness and is appropriate to the age group being targeted. The fantasy elements, by comparison, are uneven, with all the potty and animal humor especially wearing out its welcome. Interestingly enough, Nanny McPhee is the odd woman out, and not only because she's odd. The movie doesn't know what to do with her and ends up doing very little, repeating all of the same beats from the previous film in the series without adding upon it or building extra shades to who she is. If the creative intention is to keep her a mystery, so be it, but can't she at least act a little more human and personable, becoming an active protagonist in the tale rather than a curious bystander? In her own film, Nanny McPhee holds the impact of a day player.