If there’ll always be an England, there’ll always be sentimental English comedies about genteel old ladies who happen to be murderers. That’s what Keeping Mum is, and that description doesn’t spoil anything. There are no surprises in this gently homicidal farce, even if scripters Niall Johnson—who also directed—and Richard Russo don’t disclose the story’s secrets until the last act. That’s just a formality, since everything that matters is revealed in the prologue, set “43 years ago”: Pregnant Rosie Jones is arrested after the dismembered bodies of her husband and his lover are found in a trunk, and she’s sent to a criminal asylum. Just about 43 years later, a woman who calls herself Grace Hawkins (Maggie Smith) arrives in rustic Little Wallop to become the housekeeper for vicar Walter Goodfellow (Rowan Atkinson) and his family. Grace shows a particular interest in the vicar’s wife, Gloria (Kristin Scott Thomas), who’s in her early 40s and believes herself an orphan. But helping Gloria means that Grace, a different sort of Supernanny, must fix the whole household: rescue son Pete (Toby Parkes) from school bullies, chill the sex life of teenage daughter Holly (Tamsin Egerton), and reheat Walter’s libido. Gloria is so erotically desperate that she’s considering an affair with an American, a golf pro so vulgar that he’s played by Patrick Swayze. Plus, the neighbor’s dog must be silenced so Gloria can get a decent night’s sleep. It’s the latter problem that reawakens Grace’s killer instincts, but a tale like this can’t slake its comic bloodlust with one yipping mutt. Atkinson makes an effective straight man, Smith is so steely she twinkles, and Scott Thomas’ depiction of respectability deranged by passion is almost as funny here as in The English Patient. Aside from Swayze’s performance—and his innuendo-laden lines, which aren’t his fault—everything harmonizes in this cozily retro fable, which could have been produced by Ealing Studios, Britain’s postwar comedy factory. Take that as either a commendation or a warning.