Tully (Mackenzie Davis) breezes in like a waft of lavender: she's young, carefree, hippyish, annoyingly wise. It lives in the unglamorous and sleepless postpartum haze of breast pumps and swaddles.
Take Theron's work in Tully, for instance.
When a night nanny, Tully (Mackenzie Davis), a gift from her wealthy brother (Mark Duplass) appears as a vision at her front frosted-glass door, Marlo rejects her.
Marlo is less sure. "It can really be challenging when you have a teacher telling you that there's something wrong with your kid, or that your kid can't keep up".
Through Tully, the drowning Marlo works her way to the surface to catch a gasp of air. Marlo quietly dreads her impending labour, but her distracted, affable husband Drew (Ron Livingston) seems to be taking it all in his stride.
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Tully spits out lines like these throughout the film.
But the Mary Poppins-like character's abrupt announcement that it's time for her to move on threatens to bring her employer's world crashing down around her head. Of night she says, "That's the downside of living on a planet with a short solar day". Making matters worse, Margo is pregnant again - as we see when her huge belly precedes her into the opening shot of "Tully", a movie filled with raw truths about the maternal condition and with a startling plot twist that suddenly rears up out of the story and transforms everything that came before it. Their conversations steadily grow deeper and soon Tully isn't just helping Marlo rest, she's reinvigorating her life. "My body looks like a relief map for a war-torn country", she later says when asked about her dormant sex life.
The dialogue, of course, is unmistakably Cody's.
It's good to see Theron, giving one of her best performances in an exceptional career, reunited with director Jason Reitman and screenwriter Diablo Cody for the first time since the bitingly perceptive "Young Adult", a 2011 movie that never got the love it deserved.
Coming off a jam-packed year of movies including Atomic Blonde, Gringo and The Fate of the Furious, Theron gives credit to her own mother, Gerda Maritz, who lives up the street and regularly steps in as co-parent. This one, with its bold treatment of a subject with which half of the moviegoing population will be at least glancingly familiar, should be more appreciatively received.
That makes "Tully" a valuable antidote to a lot of the usual representations of early motherhood - and valuable especially to would-be fathers, who may have some Drew in them. It could be argued that this third baby is a crucial juncture of self-realization for Marlo that the previous two children didn't prompt. Then look at the birth statistics for nine months later.
"Tully", a Focus Features release, is rated R by the Motion Picture Association of America for "language and some sexuality/nudity".