KRISTEN WIIG has made a career of quiet mortification. Since creating her strange, often quirkily recessive recurring characters on "Saturday Night Live," then attaining superstar status in the smash raunch-com "Bridesmaids," Wiig has turned a relatively limited bag of behavioral tics - shy downward glances; whispered line deliveries that trail off into vague nothingness; oblique, off-center staging - into her own highly personal, mousily effective Hollywood juggernaut.

She brings all of those familiar mannerisms to bear on Johanna Parry, the withdrawn heroine of "Hateship Loveship," although here they're deployed in the name of literary-minded drama rather than comedy. Adapted by Liza Johnson from a short story by Alice Munro, "Hateship Loveship" sneaks up on the viewer, not only in the way the story takes its unlikely turns, but in Wiig's own portrayal of a woman discovering desire and, in the most subtle way possible, acting on it.

As "Hateship Loveship" opens, Johanna - who has worked most of her life as a domestic aide for one elderly woman - is starting a new job in a new town ("a new everything," as she describes it), where she will be serving as a housekeeper and nanny for a prosperous businessman named Bill McCauley (Nick Nolte) and his teenage granddaughter Sabitha (Hailee Steinfeld). On her first day at work, Johanna also meets Ken (Guy Pearce), Sabitha's father, a raffishly attractive lout whom Johanna walks in on as he's stealing drugs from his father-in-law's medicine cabinet. (All the supporting players in "Hateship Loveship" are terrific, especially the young Sami Gayle, as Sabitha's best friend, Edith.)

Observing the family's fractured dynamics with a slightly glazed but hungrily avid stare, Johanna begins to be drawn in. The question in "Hateship Loveship" is to what end, and Johnson - who made a superb debut in 2011 with "Return" - does an estimable job of doling out information and plot developments so deliberately that the audience is never quite sure what's around the next corner. Certainly they get no clue from Wiig's performance as Johanna, whose cipherlike impassivity at first threatens to make "Hateship Loveship" fatally inert, but then begins to pay off as the film heads to one of the more startling third acts in recent memory.

Before viewers dismiss that denouement as impossibly pat, they should ask themselves: Wouldn't its opposite number be just as tidy? And haven't we seen that story before? But we've never seen a protagonist quite like Johanna, who on the one hand personifies female self-abnegation at its most domesticated, but on the other embodies sheer will at its most stubborn. She knows the value of elbow grease, whether she's redeeming a dirty kitchen floor or even a scruffier human soul.