IMAGINE THE VOICE of a syrupy narrator: "What happens when a trunk murderess sets things right at a dysfunctional household? And what happens if she's played by Dame Maggie Smith?" Director Niall Johnson (Let's Talk About Sex) transplants a civilized Richard Russo script to England—the Isle of Man, apparently. Keeping Mum provides a balm to those longing for peaceful green fields and for real estate that has at last got the dampness chased out of it. The village of Little Wallop is ministered to by Rev. Goodfellow (Rowan Atkinson), whose jejune sermons are but the outward sign of a man abstracted by some underwritten spiritual crisis. He has it so bad that he has given up bonking his slender, fine-boned wife (the slender, fine-boned Kristin Scott Thomas). Distracted by her nun's life, she falls into the arms of a Yankee (hiss), a local golf instructor, played by Patrick Swayze, who wears unfortunate underwear and who looks as if he has been aging like prime rib in a meat locker.

Rev. Goodfellow, like many ministers, comes across as a nice enough person as long as you keep him off the subject of religion. He appears oblivious to the seduction of his wife, as well as to the bullies working over his son (Toby Parkes). And he overlooks the way his daughter (Tamsin Egerton) consorts indiscriminately with the local boys. At last, to correct this out-of-balance life arrives the new housekeeper, Mary Poppins—or rather, a frighteningly calm, recently paroled trunk murderess. She still has her trunk ready and evinces the ability to rationalize a necessary murder or two—or three.

Maggie Smith plays "Grace Hawkins," as the former Rosie Jones calls herself. Smith is the hook upon which this tidy but tiny film hangs. The lady's face is quite kaleidoscopic, and one can find killer malice as well as lilac-scented gentility in her, depending on how the light hits her. As in the straight-to-PBS drama Mrs. Palfrey at the Claremont, Keeping Mum intends to be a late-period example of British steadfastness in the face of American mania. Keeping Mum is the kind of film in which the extreme of sensual pleasure is indicated as the ability to sleep late—despite Swayze's meaty caresses, that's when Scott Thomas looks the most rapt when covered by cozy blankets. And only one point in the film proves extreme enough to justify its aims at being a black comedy: when we're invited to share Smith's smile at the injury of a child. The child is a bully, so I accepted that invitation.

Smith occupies the center of the film, but because of the too-well-bred script, Atkinson doesn't get to provide some drama by counterexample. He never raises a pastoral objection to the idea of killing one's noisy or nosy neighbors. Atkinson can't really gain a toehold amid the film's smoothness. He has a small portion of physical comedy, being an amateur soccer goalie who can't keep his head out of the net. Instead, Johnson forces this marvelous comedian into Dick Van Dyke levels of sententiousness. Grace fixes the reverend's marital problems by advising him of the romantic implications of "Song of Solomon." Apparently Goodfellow never heard this in seminary school. Atkinson's voice, buttering over that fulsome biblical poetry, is of a constant ookiness, compared to which murder is only a misdemeanor.

Keeping Mum (R; 90 min.), directed by Niall Johnson, written by Johnson and Richard Russo, photographed by Gavin Finney and starring Maggie Smith and Rowan Atkinson, opens Sept. 29.

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